206: Scope Rabbit Holes With Andrew Rogue

Welcome to the Automotive Diagnostic Podcast.

We're going to explore ways to sharpen our diagnostic skills, find learning resources and hear from experts in the automotive field.

This episode is brought to you by L1 Automotive Training and Keith Perkins.

If you're looking for education on module programming, j2534, eprom work, key and immobilizer, electrical diagnostics or drivability diagnostics, keith has a website, l1trainingcom that's got over 60 hours of training videos on all those subjects and more.

When I first started out doing mobile, I utilized Keith's videos on module programming and J2534 in order to get my head wrapped around what I would need for the tooling, the computers, the software setups, what kind of obstacles I would be up against when I'm out there programming modules on cars, and it was a huge benefit to me.

I continue to use the training videos that he has on his website.

I strongly recommend checking out L1trainingcom.

We have got Auto Rescue Tools and Isaac Rodel as a sponsor for this podcast.

Hey guys, if you're looking for programming laptops, you want the laptop setup ready to go for programming control modules on vehicles.

You need key cutting equipment.

You need diagnostic tools.

Isaac is your guy.

There's all that stuff available for purchase and the support that he offers, along with the purchase, has been outstanding.

I bought some stuff from him in the past.

I got my dolphin key cutting tool from him several years back and again the support has been phenomenal.

Help me out along the way with anything additional I needed to make it work for me, so make sure to check that out as well.

Again, that's autorescuetoolscom.

The link will be in the show notes.

Hey, what's going on?

Automotive World.

Welcome to another episode of the Automotive Diagnostic Podcast.

My name is Sean Tipping and I'll be your host once again for today's episode.

Thank you for joining me On the show today.

I've got Andrew Rogue joining me.

Andrew's a listener of the show.

He's a technician down in Phoenix, Arizona, or the surface of the sun, as he's going to tell us about, and he's joining me today.

He reached out on Facebook and he recently went through a diagnostic on a Chevy Malibu that had a misfire and he did come to the conclusion but the testing results that he got kind of confused him and he wasn't sure why he was seeing what he was seeing.

Now he's using a lab scope to try and assess fuel injector that he thought was causing the misfire on this engine and he got some results and again it was just something didn't add up, something didn't make sense based on what was actually the fix for the vehicle, what was physically wrong with it and what he saw on the scope.

And so he wanted to go through that with me and see if we could sort it out and figure out why he saw what he saw.

And I said, sure, I'll give you the best help that I can offer and see what we can do.

And he sent me some notes and a scope pattern so we could look at it and I'll probably post the scope pattern in the Facebook group so that you can see it too, and I think that would be really helpful.

And maybe just pause the pod right here and take a look in the Facebook group.

It'll be in the comments section for this episode and you can see the scope pattern.

It'll make more sense on what we are talking about.

Now a couple of things I want to mention before we jump in here.

First thing this is a great example of lab scopes and how they can be really powerful.

But the thing that's not talked about maybe enough is that they can also send you down some crazy rabbit holes, things that you would see with the scope, that you would never see with any other diagnostic tool.

And you may think, well, that's the problem, obviously.

Right, I'm looking at this, I see this.

This is an issue, but you would have never seen this particular we'll call it a glitch any other way.

Well, that glitch may not be anything, it may not be a problem at all, it may be completely normal, it might be equipment failure.

It's just the fact that when we get some of these scopes and we're not used to looking at particular waveforms we don't always know what's normal, what's good, what's a problem, right, and the more you use the scope, of course the idea is that you could pick that stuff out easier.

But as we're learning these things and not even just scopes, but just circuits in general, like you haven't connected up to this particular circuit on this particular car, so you don't know what's normal and what's a problem, and sometimes you can follow a thing that you think is the problem, but it's not the problem, right, and it's an important thing to remember.

About scopes, we're going to talk about that.

The other thing I wanted to mention as I was editing this episode, I noticed something that I need to point out, just for not only Andrew and I did reach out to Andrew the other day and after we talked, after we recorded and I talked to him about this, but I wanted to point out for everybody listening too, because it's important to know this.

I didn't catch on to the line of thought while we were discussing this, but there's a point in the podcast you'll hear it where he mentions that voltage is low because amperage is high, and that can't happen, right, and we're discussing the potential of an injector that's drawing too much amperage.

That would cause low voltage.

That's not a thing.

That's not how electricity works.

You go back to Ohm's Law and the relationship there.

In order to have adequate, or even more than normal, amperage, you have to have adequate voltage.

If you don't, you're not going to have the amperage.

That's it.

That's the only way it works.

So just keep that in mind as you're listening.

We don't mention it during the show, but that is a thing that I'm sure many of you do know, but I wanted to make clear just so it's not something that was missed.

Anyways, I really enjoyed this.

Andrew's a very well-spoken, intelligent guy and I'm glad he came on the show.

I think everybody else will enjoy this as well.

That out of the way, let's jump in.

So how's it going, andrew?

Pretty good.

The heat in Arizona is not something I'd wish upon anybody.

What part of Arizona are you in?

So I'm out in a little town called Buckeye, which is the westernmost suburb of the Phoenix metro area, so I'm right.

Locals affectionately refer to it as the surface of the sun.

It has been miserable, Although today did cool down.

We only, I think, got up to 108 today.

So geez, oh man.

Yeah, I have some family that lives in Phoenix and they've said the same thing.

They have a cabin.

I'm not super familiar with the area, but it's way up in elevation as opposed to Phoenix, so it'll actually snow up there and stuff which I didn't know that you could do that in Arizona.

But they said they would go up there now and it's still 90 degrees or whatever.

And then, yeah, you guys are at 120 or, like you say, the surface of the sun, yeah.

You get a little farther north and it's a lot more bearable.

How much AC work do you guys do Just all day long?

We do a ton.

It's almost it's frustrating from like a.

Because I am a technician, I do work for a shop.

I'm aspiring to someday own my own operation and I'm not quite sure if I want to own a full service shop or if I want to go kind of the route that you go of doing mobile dyagon programming.

I really enjoy the dioxide, but we get a ton of AC work and we'll have things like you know your brakes are at, you know one or two millimeters of pad life left and your AC is broken and they only have money to fix one thing and they're fixing the AC.

You know you got belts showing on the tires and we're not fixing the tires, we're fixing the AC.

So it's like people always prioritize that first, even over like safety concerns with a vehicle, which is frustrating from like I care about like the big picture which is maybe a fatal flaw.

But yeah, we do a ton of AC work.

Like it's mind numbingly, it's annoying, like I like doing, I like doing dyags.

I don't like AC.

I mean it's like it's got a leak, great Like.

Yeah, right, yeah, sometimes you get throwing some electrical stuff there on the AC, or at least I get some of that doing the mobile thing.

But it was the same thing when I was tech up.

Here is come summertime, as soon as we hit that first 90 degree day, people will dump absurd amounts of money into their air conditioning system when, like you say, you know they've had this oil leak.

Yeah, suspension's falling apart.

You need brakes, you need tires.

It's all rusted out up here.

No, get that, get that compressor running.

And we get the people who maybe it's just like a hot summer and so we go stretch this period of time in the winter where nobody uses the AC, and maybe it's a kind of a cool summer and they didn't really use it, and so that compressor, that AC system, hasn't even been on in a year plus, and now they go to turn it on like, oh, does it work?

And they just come in, can you just recharge it?

And maybe, but also maybe, the compressors locked up and the belt fell off and there's a hole in the condenser.

And yeah, it's crazy stuff, but there was always good money in it.

Man, that was one thing about AC, that is true.

We've got a problem vehicle that's in and out of the shop right now.

It's a 2014 Ford Super Duty and I think we've spent about $4,500 in AC.

We have replaced every component in the system and, without fail, it goes two days after it leaves our doors and it stops working.

And this last time it left, I think it went a day before it started working and we had it like it was done and we had it in the shop and we let it sit there and run for 45 minutes.

We had a couple different guys take on long road tests, like everything you could do to make sure it was fixed, and we gave it back to them the next day it stops working.

So that's, it stops working as in leech out or something electrical.

Oh OK.

Well, let me rephrase.

I don't know, I'm not working on it.

Oh gotcha, that's the, I guess the frustrating, which kind of leads us into the reason that I wanted to come on here and talk to you.

And that's doing like it.

Advanced electrical Diag is not something that really anybody else in my shop does, like I'm the only one that.

Ok, like we have the I've got to use scope, but then I've the only like real scope that I have.

Besides, the use scope is it's a what is?

It's a snap on Triton little two channel scope, which is better than nothing, and it was was really handy with this, this diet that I was working on.

I guess this would have been yesterday and and so it's stuff like that is like I don't know if it's an electrical issue with that AC concern because, like, we've done everything and it keeps having this intermittent issue and it almost feels electrical to me.

But I'm not the shop foreman and the shop foreman has been working on it and he kind of has a bit of an ego and he doesn't want to take that one down and it's like it's always frustrating in this industry when you get people with egos.

Now, granted, I have a big ego and I can be a bit of a prick, so it irritates me and I do it.

There's a slight advantage to having an ego doing what we do Like you need to have confidence in yourself and it can be a good thing.

But yeah, you can go overboard with it and it can be to your detriment pretty easily too.

So there's just a balancing act there of figuring out what's the what's the right amounts and when am I being a dickhead?

Exactly, exactly.

And I?

I miss that balance probably too often, might.

I'm not, I'm not the well, I am the favorite tech in the shop.

Everybody loves me, at least I like to think so, yeah.

That's what we all think.

Are you at a independent shop or dealership?

Yeah, I'm at an independent.

I've been at independence my whole career.

I work.

I work for a small independent.

Right now We've got I think we're running we'll call it four and a half techs, because I've got, I've got our.

Our foreman is kind of half half is like half in production as a tech and half just in management.

And then we've got I think we've got a fifth tech that's starting on Monday, so we'll see how he does.

But yeah, we're a small, small independent shop and it's we are also the shop that, like, we get all the problem cars from everybody else.

So anytime a car's been through two or three or four different shops, it usually ends up coming to us, which is which is great.

Sometimes it seems like we usually end up losing our shirt in one way or the other.

As far as making money on stuff because we'll spend, the hard part is is charging for Diag time when, like, the Diag took forever, not because it was a hard dive, because of a tech's lack of experience.

You know, like if a tech floundered for eight hours to conclude that a fuse was blown, it's like is it really fair to charge a customer eight hours when you should have checked the fuse first and that's a whole nother?

I don't think so.

Yeah, that's a whole other discussion, but yeah, so I kind of want to move into this.

This, I guess we'll call it a case study.

It's kind of an ongoing case study, since the car is still at my shop.

This is a 2017 Chevy Malibu LS with a 1.5

, a 1.5

turbocharged, direct injected.

I think.

It's a four cylinder.

Yeah, okay.

So this car came into the shop initially, let me see, I got it in front of me Initially, came in as a crank nose start and the I didn't look at it initially.

Another tech looked at it and through the course of their Diag, we found that the exhaust camshaft had actually broken in some fashion.

I'm not sure if, if, like, the reluctor wheel in the back of the cam broke or if the cam itself had an actual catastar failure.

So what did we do?

Sorry, we threw all the notes here and try to make sure I get the storyline correct.

So we found the broken cam, pulled the valve cover, found the broken cam and so we replaced the broken cam and then we did a full OE timing kit.

So it got a, a vac, that's a gasket, all the chains and guides and tensioners and all that sort of stuff, and then they had a misfire.

They stayed at a misfire on I think it was cylinder three.

They put a single fuel injector in cylinder three.

The misfire moved to cylinder two, that they put a full set of fuel injectors in it and then it ran fine.

The story that I got was it drove fine for 10 miles and then developed a dead miss on cylinder four, and that's where I got it.

So I guess kind of what I want to do if, if you're good with this, is I'm just kind of going to run through kind of the process and what I did and then and maybe just kind of run through it real quick and then and then kind of talk about maybe where where I could have done something differently, maybe if I misinterpret, because at the end of the day the call that I made on this was wrong and I'm I'm trying to figure out from my own education where did I go wrong in my process

and what or did I?

Did I miss interpret test result?

Was there something I did wrong?

So let me just run through this real quick.

I know you already read it, but for the benefit, of everyone listening.

I got to do.

I got into it had dead miss, the flashing check engine light.

I I scanned the vehicle, all the relevant codes in the PCM.

There were a bunch of coil circuits and jet or control circuits and a lot of previous testing had been done, some of which were the engine running.

So I assume that most of these were set with just throughout the course of testing and weren't actually relevant to the issue.

There was one there was, I think it was our, our misfire code.

I looked over at the freeze frame data and found that fuel trim was indicated a super rich condition when when it set that code.

So positive trims, yeah.

So the the freeze frame showed a plus 17 on the short term and then zero on the long term.

And then when I looked at the data with it running it was like plus 27 plus 25.

So like way positive trims, um, yeah, plus 26.

And then plus or long was plus 26, short was plus 33.

So I went so it had set this P zero 300 misfire code.

I went and looked at the misfire accounts and cylinder four is a dead miss.

Every cycle, any RPM it's dead like dead dead.

The cranking rhythm sounded okay.

A quick, I guess, side note is the yeah Previous tech slash shop foreman kind of got together and they spent like six or seven hours messing with this thing and they concluded that we needed to remove the cylinder head and inspect for a valve actuation problem because they had a Running compression test that was with erratic results is what I was told.

But like nobody wrote anything down, nobody made any actual notes, so it's kind of hearsay, because this was like three weeks ago.

But the cranking rhythm sounded normal, just like cranking on it.

I Removed cylinder for spark plug and found that it was.

It was wet, but not like soaked.

Like it was wet, like we weren't getting Spark is what it looked like.

I've tested spark coming out of the coil.

There was good spark coming out of the coil and I swapped it.

I swapped the coil with the one next to it.

So I swapped it with cylinder three.

So cylinder three is what we're doing a lot of swapping with, because cylinder three is known good, cylinder four is Unknown or known bad.

So I swapped the coil with cylinder with cylinder three good, clean, bright spark out of both coils.

Spark is, spark is not.

It's not a real issue.

So my conclusion from that is spark is being sent the spark plug but for some reason we're not igniting the mixture in the cylinder.

Went ahead and did a static static compression test, just cranking compression test.

Cylinder four tested at 235 psi, cylinder three tested at 235 psi.

So you know 10, 10 pounds of difference in cranking compression between runs, fine and dead miss every time.

And Then I went ahead and did a running compression test again.

I'm I don't have a pressure transducer to do this with the scope, so I'm just doing it with a, just a gauge.

I'm watching the needle bounce and kind of eyeballing for that fraction of a second when the needle hits the top number, cylinder threes peak compression was 120 to 130, so roughly half of what static was, which, if my Recollection is correct, that's normal.

And then cylinder four was the same thing 120 to 130 is the peak.

So the conclusion of that is there's no measurable difference in compression between cylinder three and cylinder four.

So known good versus known bad, compression is the same.

Compression is not our issue.

So I got to break out my favorite tool in the shop Well, my favorite tools my pocket screwdriver, but I got to break out the I got to break out a lab scope for this one.

I Listen to your your everyday carry of a diag tech episode today and I was like, yeah, I'm the only guy in my shop that carries the pocket suit ever in his pocket.

I use that thing all the time, you've always got the solution right there.

Exactly so.

The injectors have like a sub harness right on the top of the fuel rail.

There's nice big connector and you can get to all the pins to back probe it.

I Didn't have a good way to.

I'm not opposed to piercing wires, especially down here.

Especially it's like it's dry, we don't get salt, it's not.

I don't have problem piercing wires in this case.

Back problem was just easier.

So I.

So these fuel injectors are controlled by the PCM.

One side switches a ground, one side switches a.

There's a discharge capacitor that spikes voltage up to like 65 volts to hold the injector open and then it regulates it like 12 or 65 opens the injector and then it regulates it about 12 to hold it open and then it closes it.

Okay.

So I scope number three, which is just looking for a known good pattern.

I actually, because it's a two-channel scope, I put hooked one channel, one channel, into number three, which is my known good, and then one channel into number four, which is my, my unknown, and what I found was number three's got a good, a good, clean scope trace.

You can see the, the voltage ramp up to like 65 volts and then you can see the pulse where it Cycled it on and off and you can see how far, how, how long the injection pulses.

Everything looks great.

Number four, injector pattern, if you zoom way in, does the same thing, except the spike only goes up to one volt, so the index takes 65 volt, one volt.

So the pattern was there.

It you could see the ramp, you could see the spikes and they using a Trigger.

I was able to see that they like lined up with each other.

Just one only spiked up to a volt and one spike to 65, but something was happy.

What I was able to conclude from that was that the PCM is not Disabling this injector like it doesn't see a fault, and it's turning it off because I'm still seeing some amount of signal that tracks With what a normal signal looks like so Like it was flashing right, the check engine light was flashing.

Initially it was not.

It was not at the time that I was testing this, okay, it was just, it was on solid and it just had the 300 coated.

Hadn't set the 304 for the cylinder for misfire yet.

Okay, and I Checked couple.

I check the other two fuel injectors.

Everybody's it, everybody's at 65, except for number four.

Is is low, there should be.

There's a supply side and a control side and the PCM switches, both of them.

And looking at a wire diagram on Mitchell showed the control side or what.

What the wire diagram showed, as the control side is where I was seeing the 65 volts or seeing that that spike to 65, I Scoped the.

The other side of it, which Should, I think, I think, according to the diagram, is the supply.

I'm not sure exactly how this Works as far as which way, I don't know how current flows, but there's, there's two sides.

I scope one side, I get 64.

The other side, the pattern, is it like it's?

You can see it moving and there's a repeatable pattern, but it's like one or two volts and I can check both.

Number three, which is known, good.

Number four, which is known, or unknown, or known, or that's our problem hole and One side they look the same the other side.

One spikes 65, one spikes to one.

Okay.

I measured the resistance through from that sub harness down through the injectors.

I cylinder cylinder three are known good came in at 1.8

ohms and cylinder four, which is our unknown, came in at 1.7

ohms.

So okay, resistance wise were really close At that point.

I ruled out, ruled out an injector, I pulled the.

I pulled the PCM connector and I load tested both, both legs.

Because this wire comes from the PCM, it's a one piece of wire.

There's no connectors until the sub harness connector.

I load tested both wire, or both both wires of the circuit, and then I also tested both for a short to power, a short to ground, and Found no issues.

Yeah, and there was there was some.

There was some corrosion on another pin.

There was a sensor ground that I cleaned.

I don't didn't think that was related to it, but I saw corrosion.

I cleaned it.

It's just kind of a thing and that that didn't.

After I did that, nothing changed, so that that corrosion wasn't causing our problem.

I also checked resistance through with from the PCM down through the whole harness and found resistance within a tenth of an ohm of my test of the sub harness.

So I checked everything and, based on all these tests, I recommend replacing the PCM because Everything else is there.

I'm just not getting driver actuation out of the PCM.

Put a PCM at this morning and had the exact same symptom.

Okay, new, newer use, just curious new new from the dealer.

Okay, so Went back through, rechecked, I Rechecked all that, I re, I rescoped it Because at this point my boss is like, oh yeah, you did, you called it wrong, it's, it's in the head.

And I'm like, no, something wrong, there's something electrically wrong with this, because when I scope this wire I've got a good, I've got 65 volts, when I scope this one I've got one, and these should match.

And so we kind of talked it through and concluded the only other thing on this circuit that could possibly be drawing it down is a fuel injector.

So we ordered a, we got, we got a new fuel injector and then just plugged it.

Didn't install it, just plugged it in to see if our spike would come back.

And I had.

I had to clear the codes because we unplugged it with a key on and it set a circuit code and then it turned off that injector, but clear the code with a new injector plugged in, started the vehicle up.

You could feel the injector, the new injector, clicking in your hand and my scope, but I've got 65 volts back at the at the injector sub harness.

So okay.

I'm basically.

What it happened is somehow the injector I Shorted is the word that comes to mind but was drawing more current than it normally would and Was pulling that voltage down.

But I guess what I'm.

What I'm trying to figure out is how does that even work?

Like my, I can't understand in my head how that could be the case, and none of my testing would have given me any indication that that?

yeah, so I was looking up diagrams and stuff while you were talking to so I could get a feel for the setup, and Well, there's a number of things that popped up in my head as you were going through that.

Is there any other Things that you wanted to point out on that before I jump in?

I'm.

Do you want me to give you the what I, what I found when I put a new injector in it?

Or, or do we want to?

Let's?

let's hold, let's hold off on that, okay, yeah.

Okay so I Know, when I go after GDI stuff, when I first Got my hands on a GDI car and I had a scope at the same time, I'm like, yeah, I'm a scope, the shit out of this thing, and I remember it was actually a Volkswagen, it was very first one that I was able to hook a scope up to one, sorry, and look at yeah, look at the Injector

waveform, and I'd done it like I did many, many other port injectors.

We're looking at voltage and I was very confused by how you could see control on both sides and it made.

Where do I reference my scope in order to get a you know waveform?

That makes any sense to me, especially considering what I'm used to, because, again, like you say, they control on both sides, and Something I'm thinking about on this one is they share a path for the boost capacitor in a lot of cases between a couple cylinders within the ECM, and so you'll see some activation from another injector on.

You know.

Let's say, I don't know if these ones do share in this application and I don't know which ones if they do, but let's say, two and four share a boost capacitor within the ECM.

You could see activity from one on the other, depending on which side of the circuit you're on, and so that makes it even more confusing.

So what I do now, when I must try to assess an injector operation on a GDI, is I will go to amperage First and foremost, so I put an amp clamp around either one, doesn't matter, and that's the the beauty of it, it doesn't matter, it's just which way I flip it.

But then I'm looking at the amperage just for that specific injector and I'm not so worried about the voltage, unless, unless, okay, the amperage points me that way.

And now I want to see what's going on on it.

But I Want to see the amperage and it gives you, in my opinion, a clearer way form of what the injector is doing right.

It's an output, is doing work, it's it's drawn some current right, yet it's only a couple ohms, so it's gonna be really drawn some current, especially with the higher, the higher voltage, the boosted voltage, and so you can tell a lot by what's going on, and especially because you have, you know, three other known goods right there and you can go and compare.

So that's, that's the way I like to look at it, because that control on both sides and a potential shared path and then the ECM between a couple cylinders can really make things difficult to digest on.

On the voltage side of things with a scope, not to say that if you really know that application and that car that you can't use it, I just, for me, I find amperage easier to look at.

Now that, all being said, and and obviously it'll get to what you end up finding, I'm just wondering if the ECM was Actually shutting that down and maybe you were seeing voltage or something that was from a shared shared leg of the.

Yeah, yeah, I have to look at the, the scope.

Actually, I think you sent me the scope.

Yeah, I sent you that up and see a picture of it, so something something that I struggled with that I think would have maybe helped to make this diagram a little clear is, like you were saying about a A boost capacitor that is shared between one or more cylinders how, where do what?

Where would I go to find that information?

Because I went digging through service information.

I couldn't find any information as far as, like, what is the internal of this PCM circuitry look like?

Yeah, as far as how?

yeah, see, and I actually I pulled up oh, that didn't fix, just booted me off I pulled up the OE diagram because the redrawn Definitely doesn't show you much of anything.

What's going on inside of the, the control module?

It just says, you know, control high, control low, the, the OE diagram actually shows you a Basically a high, low side.

I don't know if that's the diagram you were looking at, but it'll show a high and a low driver.

But it's your generic GM Symbols within the ECM.

So on one side you have the dot with the line through it and then I switch below it which is indicating that's power, that's GM's hey, we have power here.

And then the other ones they switch to the symbol for ground.

But the issue with that is is, if you're questioning it like you are, that's not actually what's going on inside of there.

And the troubling part for so many technicians out there is yeah, I want to know how they are actually Connected within that ECM.

How are the circuits actually driven, what's going on inside of there?

And If you go way back To the 90s wiring diagrams, there were manufacturers that would give you Like that level of detail.

You know they'd show a lot of the resistors and the circuitry inside of the PCM and they kind of went away with that.

For what reason, I don't know.

But man, it would be really, really nice to see some of that detail, because I Obviously this thing is not just powered on one side and ground on the other.

I mean, even if they each have their own boost capacitor, that's, that's in there and it's not labeled in the diagram, so you don't even you know necessarily know, yeah, cuz I I just pulled it up just so I could see and track what you're talking about.

Okay, I had looked at that, the identification, the OE, the OE diagram, and and that's how I was able to conclude you know it's that it switched on both sides, because this diagram clearly shows that.

But then it's like you can't the wire that switches the power doesn't tell you where that wire goes, it just disappears and so, yeah, the other thing I was gonna look up here was the description operation, and maybe you already did that.

I was curious to see if they outlined within their how the injection system is set up.

Yeah sometimes they'll give you a little clues.

Yeah, so it says, as the ECM supplies a high voltage supply circuit and a high voltage control circuit for each fuel injector.

The injector high voltage supply circuit and the high voltage control circuit are Both controlled by the ECM.

The ECM energizes each fuel injector by grounding the control circuit.

The ECM controls each fuel injector with the six with 65 volts.

This is controlled by a by a boost capacitor in the ECM.

During the 65 volt boost phase the capacitor is discharged through an injector, allowing an injector electrical opening.

The injectors hell open with 12 volts.

So that sounds like it's one, one boost capacitor and then the ECM directs that to an injector Like there's only one and that's.

I Suppose that's possible again, without actually going inside of the module.

You don't know.

Yeah, like, how do you and obviously I know you, you dabble a little bit in in modules and I, I don't, I don't.

If the module is bad, I put a new box in it.

That's that's the extent of my.

My module works was like I, I don't know, and that's I don't know.

If there's, there's really a fix other than trying to convince manufacturers to give us more information, which isn't gonna do and it's any good, right.

But yeah, like if I feel, like if I had a better idea of how this system works inside the ECM, if, for example, my conclusion was there's different, there's different boost capacitors and the boost capacitor that runs cylinder 4 is Bad.

That's why we're still getting some actuation but we're not getting the full Amplitude as far as the voltage that we should be getting.

But if and in reading through this again, it almost sounds like it's saying there's only one boost capacitor but if, if I had a diagram that showed that, or if I knew there was only one boost capacitor, I could, I could shoot down that, that Theory, because if there's one boost capacitor and it works on this injector, then it should work on the other injector.

Right, right.

The other thing I'm looking through here is is Sometimes you can find some information on the system, and this is particular to GM.

Gm is I don't I don't know if good is the term that I would use, but it's very common for GM to hide the System description or the detail about the systems within the definition of a trouble code, and they'll they'll give you little bits of Detail that is not found in their normal Description operation, and so I'm just glancing through right now to see if there's anything that.

Yeah, and even the other thing was that I didn't have, there were no, there were no codes other than the misfire code or codes.

It did end up, it did eventually set a 304.

Yeah it was that on four but there was no.

There were no circuit codes for any, any fuel injectors or anything like that.

And typically and maybe I'm, maybe I'm you talked about an episode like when I first started listening to this podcast that sometimes, like having some information is not, is almost worse than having no information, and that you know just a little bit.

And so in my head I'm thinking, if there's no, if there's no injector circuit code, the PCM has run through all of its self-tests and all the things that it monitors and it's not seeing a problem Circuit.

Since I don't have a code, and the lack of code is not no information, it just it rules out certain things, and maybe that assumption was wrong.

I don't know.

I mean, I do know, I know now, but I don't.

I it's like I now, today, I know what the solution was, I know what fixed this problem, but I can't wrap my head around when my process went wrong, because it ended up kind of being like we shot gun an ECM that didn't work, you know, kind of a thing and and I don't understand why and that, and that bothers me maybe more than it should, but like I want to understand what went wrong, so that the next time this happened, next time I have a diagram like this, I

don't get there, I don't have the wrong call.

Well, I can say, if you know I had gotten to the point where you were at, one of the other things I would have done, and I can say this only because I've been in a similar situation.

I actually I had an Audi that would.

It was an injector problem and it was shutting down the circuit to drive the injector.

And this was a GDI, there's like a v6 or something, and it was intentionally shutting down the circuit.

And, boy, I don't recall the codes, I don't have that in front of me, but there were codes kind of pointing in the right direction or at least so that there was an issue with the injection, the injectors.

But I Powered up the injector by itself, right.

So I took the computer out of the picture and I just sent normal Battery voltage and ground to it, right, obviously they're supposed to you to get over the high pressure.

They boost that voltage up.

But you can still send power and ground to them, as long as it's not one of the crystal stacks, that that's a different animal.

But for a regular copper winding Injector on GDI, send 12 volts to it, measure the amperage and again You've got X amount of known goods on that vehicle to compare to and see.

And this one spiked the amperage.

I Wish I had my notes in front of me.

In this one it was much higher than all of the other ones, is what I can say.

Noticeably, I was just measuring amperage, connecting power and ground, and this thing was way high and the computer recognized that and so it just shut down the circuit.

I'll let you go with what you found and I'm gonna see if I can find my notes on that Audi.

Yeah, I, just while I'm sitting here looking through information on on Mitchell I, I I'm looking through the OEM test flow chart for the fuel injector coil test and I'm looking at what it, what it calls for to test.

It says disconnect it, test for One, one point three to one point four, four ohms Between the two pins and if it's not within that, replace it.

Now, my, my measurement when I checked this was not within that range, but the known good next to it was also not within that range.

Okay, but yeah, I just found this.

I didn't see this yesterday when I was looking at this, but that but even then I don't know that would have changed the, the direction that I went as far as, as far as a call on that, because I, like I've got a known good.

This one works this one works every time and it works normally and it's at one point eight.

That is technically out of spec, but it works, and if the one next to it measures the same, you see I'm going with that like yeah, yeah, and so number of temperatures there's a lot of temperature.

There's a lot of temperature.

There's a lot of temperature, there's a lot of temperature.

There's definitely a factor, you know, when you're looking at the resistance resistance is something like that and I'll use a resistance value of Something that does work right.

I try to evaluate components Electrically speaking, is are they sending information or are they doing work?

And I treat them a little differently and I think about them differently when I'm testing.

Right, so, an injector, obviously it's doing work, it's drawing some current and so not that I won't own check it, I will.

And again, if they give you a spec, why wouldn't you?

But I'm going to just kind of take that as one piece of information about it.

And again, in a situation like that, I'm going to be sending power and ground to it to see.

Okay, let's force it to do work and see what happens.

Because you know maybe once, because because your own meter sending what like three volts through the thing and almost In a minuscule amount of current, whereas this thing's meant to handle potentially.

Six, seven, eight amps of current.

Yeah, I just found my notes on this and, by the way, so you sent me a bunch of notes on this car.

That's fantastic that you do that, because it just for this reason, like this, was Over a year ago that I looked at this Audi and I made myself some notes.

But it's good that I can look back at this because I didn't remember any of these details.

Yeah, this was an 07 Q7, 4.2

liter.

I did have a code.

It was a p 21 47, group B, injector circuit, power supply circuit, open, shorted.

That was the code.

So that did, awful, I yeah, right, but yeah, and that's more a direction that I think you had with this one.

But yeah, what I ended up finding is that there's two injectors that share Multiple injectors, share power feeds, but it's in groups of two, and seven and four are Basically the ones that pertain to this code, right.

So you have to.

Then you have to determine as attack isn't seven or is it four?

And what the ECM would do is just quickly Pulse the circuit and then it would shut both of these down.

So then you had to determine which one it is, and I did that part of it.

Wasn't clear that it was seven and four and that either one could cause it.

But I got there eventually.

I do have a note in here.

So for anybody working on one of these, the redrawn wiring diagrams are wrong.

Imagine that.

So use the factory if you're doing this one.

But I did own the injector and let's see, the good injector should be two ohms and Five to six amps.

I probably had a discharge battery there and then the shorted one was one ohm and closer to ten amps, and After replacing that, that one that drew ten amps that was only at one ohm, that fixed the problem and then the computer didn't shut down the circuit anymore.

So anyways, yeah that, yeah, so I'm the one that superfine with that, that method of driving, because I so I Specialized in like diesel or light-duty diesel.

So I like pickup truck diesel is what I specialize in.

So Duramax has run the same way where they group injectors together and it's I they have a.

There's a super common problem, I think it's like the number a injector pig tail goes bad.

But it sees that the ECM sees that problem and it shuts down the group and so you lose two injectors.

And if you're not, you know, familiar with it, you're gonna chase your tail trying to figure out which injector it is.

That makes sense.

There's information out there.

You can find it, especially if you have a code that gives you a direction.

This was like there's no code, this is dead, what's wrong with it?

Figure it out.

Sure, which is fun.

I like, I like a good, I like to be able to like, stretch my diagnostic muscles a little bit right and get to do it, because I, I'm a line tech, I work on everything.

So I mean I, you know, I'm doing cylinder heads on a 2006 Ford diesel right now.

It's like I do big heavy work, I do a little bit of dyag, so I like, I like the good dyag.

So basically, we found that when we plug the fuel injector in, our our voltage came back, and so we went ahead and and replaced it.

And here I'm actually just gonna real quick so you can really appreciate this if you pull your phone out.

I'm gonna send you two pictures right now.

And, and Our new tech is the one who put the injectors in and when he installed the new fuel injectors, he did not remove the old fuel injector o-ring from the fuel rail and what happened is, when he jammed the new injectors into it, the o-ring came apart and there is o-ring debris down inside of the number four fuel injector.

Okay, okay.

So, you can see that down in the middle, yeah there's like a little chunk of rubber down in there, so I Can't really wrap my head around why that makes the injector not work.

Another just side detail I don't have an amp clamp that talks to a to a scope.

They can read that kind of low amperage, so that wasn't a A test option available to me sure, and but I like I wish it was, because I would really be curious to see, because, if I Don't know, like I really wish we could, we could see what that, what that amperage ramp looked like.

Yeah, because I would assume that it's gonna be drawing more more current.

But how does, how does a physical clogging of the injector lead to it consuming more amperage, so much so that it draws?

the voltage down to a volt.

Well, I See, I'm still hung up on that.

The computer was shutting down the circuit to save the cat and, and maybe I'm wrong there, but that's my good that way, if you just didn't explain any of this other stuff and just ask me up like, well, yeah, I probably just shut the circuit down.

So, and again, maybe what you were seeing is voltages residual or connected to another circuit.

Again, we don't know the inner workings, and so that the computer just just shut it off because it saw a misfire and Once well, okay, so well, no, because when I?

but when you plugged in the new injector, it came back.

It would be injector just sitting in my hand and plugged in.

So now the circuits doing what it should and our voltage Came back, even though we still had the dead miss on four.

Okay, okay, now, okay, and now I'm thinking through this.

When I have that potential situation where I'm questioning whether an injector is shutting down a Circuit, I will do a key cycle right, and when you first start the engine it should go back to pulsing that circuit and that for a short period of time and and then it wants it determines that, hey, we have a misfire, then it's gonna turn it back off.

So I don't know, in your scenario, how you know the, the series, the sequence on how it was tested, or if that could be a Possibility.

I don't know how long, how long you let it run with the new injector plugged in and it running.

It ran for probably two or three minutes, I mean it was.

It was more, more than a minute Okay.

I would think of it if it okay shutting it down because it saw a misfire.

I would think that it we probably were past that and that threshold where okay it would have seen a problem and shut it down.

So what I would be curious on is that injector that was full of ordering stuff is Just, like I say, operating that thing on the bench with 12 volts and see what it's doing, and now you could see it being physically restricted.

But it's not a, it's not like a motor, right, it's not.

We just slow down a motor, you're gonna draw more amperage.

This is very different.

This is Electrically speaking.

That injector hasn't changed at all, unless I don't understand like.

That's what I don't yeah.

Like I can.

I can see a problem.

We put a new fuel injector in it, our misfire on forward, one away, and now it works fine.

I've got a misfire on cylinder two.

I did a quick, a cursory look through them.

I didn't see any debris, any of them.

But now I've got a misfire on another cylinder.

So we've ordered up, we're gonna swap out, we're gonna do the three more injectors and get, give it fresh injectors without the overing degree.

But like I don't, I can't wrap my head around.

How does a physical restriction in the inlet of a fuel injector Cause an electrical issue like what I'm seeing?

Yeah, I.

If my gut reaction to that is it can't, unless it were to physically damage the injector in a way which damage the windings, which I don't think is the case because of.

If that was to happen, your resistance value would be off that, and that's the thing, is like your own check is very valuable right.

So If I understand the way this injector works and I haven't actually sliced one apart or seen what they look like inside, but it's, there's a, there's a needle and a little like a pencil at the bottom of it and there's a needle that sits into a seat and when it energizes that magnet, it pulls.

It pulls that needle back from the seat, fuel sprays into the cylinders, it it lets go of the magnet, the needle closes like there's nowhere.

There's nowhere in the body of this fuel injector where debris could Come in contact with the electrical winding in the no oil.

So, and even if I'm looking at a picture one right now, I guess that I guess I could have googled that.

No yeah, it's not showing you the inner workings of it, but I'm just looking at the body and it looks like you're very typical looking Gdi style solenoid injector where it is just a coil of wire around the, you know, the movable, the pintle and the core of the solenoid.

So, like nothing there's no, really special.

I just there's no moving parts, because obviously something moves so it injects fuel, but there's no.

Like I work with.

The acronym is Huey hybrid electric unit injector on on older diesels where there's like you have high pressure oil that moves and there's a solenoid that controls high pressure oil and there's a piston that moves and that pushes on, like that has a bunch of moving pieces.

This injector does it.

There's one part that moves.

When it gets elect, when it gets current sent to it, it pulls that piece back.

Yeah, fuel goes in, it lets it go and closes it.

So how does it?

Especially especially debris that is, you know, I mean it's an o-ring, it's not that hard, so it'll.

It'll restrict flow, but it's not, it's not like you're dropping sand down.

That could, you know, damage some yeah, this injector.

But that's the thing is.

Even if a One of these injectors, what if you welded the tip of this thing shut?

It will not change the amperage amount Right out of the injector, right, it's not.

You do that to a fuel pump different story, but an injector, that's not going to be the case.

Doesn't care what the physical is doing.

It's just an electrical winding and yeah current.

It does it, it creates the magnetic field and it pulls on whatever.

I think that's all it does.

It doesn't know, hey, this restriction, the inlets or the supply side of this component.

So Now I'm just kind of thinking outside of the box here.

Is there any possibility that you had the scope like maybe on the wrong scale when looking at that control circuit in reference to the other one, right like the volts per division?

If they were in the wrong setting it might show you, you know, a lower voltage than what appears to be a lower.

So I had it set up.

I'm grounding my scale off battery ground and then I ran my scale in the snap.

One sets it up and it gives you the way you select your scale.

Is it's like I put it in a 100 volt scale?

It's 100 volts from the bottom of the screen to the top of the screen or the bottom of your scale to the top of your scale.

So I run it in 100, I can see the spike up to 65 on the one, and when I run the other one at the 100, you don't see it at all.

There's just like some static in the bottom.

But if I, if I change that scale down to like 10 volts between top to bottom, then I can see the.

I can zoom in on it and see that current ramp or it's not a current ramp the voltage ramp, but yeah, yeah, the voltage spike.

But so I know I know our wavelength was measured.

Like I know when I can, when I overlay them together, I know I'm using the same scale and you can.

I'm pretty sure we can actually see it in the picture that I sent you.

Yeah, let me.

Let me pull up the picture that you sent me here.

It's all sideways.

Oh, you can't quite actually know you can.

So the, the yellow trace, which is known good, to green is known.

You got that on a 50 volt, yeah, so you can see it goes off the screen and then the greens on a 10 volt and it's barely moving at all.

So you do have them on different scales.

But yeah, just just for the sake of this be taller.

Exactly, the green should should match, and obviously you can see on.

I guess it's the bottom, because this picture sideways.

I apologize, we're a little bit, we're a little bit separated, so our yellow starts a little bit higher than the green, just for the sake of clarity of the picture.

But yeah, we at this volt.

At a 10 volt scale, the green should be off the chart high, like I mean you should.

It's just you'd see that you'd see it start to ramp up and then it would just go off the screen because it's so much higher than 10.

Are these so what you're looking at here?

This is the engine running, obviously, and two different cylinders.

Yes, that's correct.

Yeah, so yellow is cylinder three, which is not misfiring.

Green is cylinder four, which is firing.

They shouldn't be happening at the exact same time.

That that's not how.

That's not how the engines work.

Yeah, I think they are there.

So for everybody listening and I know this is audio only we're looking at a scope pattern of two injectors right on top of each other, and they're right.

The one in question is much lower voltage than the other, but they're perfectly aligned, which can't be the case for two different cylinders on a four cylinder.

You ever have one of those life moments.

Well, I'm hoping I can help you.

I just had a light bulb because I saw something on the scope.

So I actually put the ECM in it and it still had a misfire.

I put the scope back up, but I only hooked up one.

I hooked up one, one set of wires to it so I had a yellow trace.

I didn't have a green, or the green trace is not plugged into the scan tool, it's sitting in it or plugged into the scope.

It's sitting in a drawer.

And I saw that same pattern on the green, with nothing plugged into it.

Oh okay, which like just clicked in my head.

So it's got to be something picking up from the injector circuit up there.

Yeah, it's honestly, it's probably inside the scope.

It's doing it, I'm not sure how or why that's potential, or it's picking it up like leads, you know, laying on each other, or something like that.

But if I thought this morning without the other one, plugged into it, that's true.

So, yeah, I would be in the, it'd be in the scope, or I'm just thinking maybe even on where are these?

Where is the scope grounded?

Just on the battery, or yeah, this is in this.

In this picture, the scope is grounded to the, the negative terminal on the battery, so I'm clipped right onto that.

Okay, all right, terminal so, but that would make sense.

That would make sense, though, if it's not, if that, if this test is faulty, because that's not actually what we're seeing.

Yeah, on the green which is let's.

When it was hooked up to the car, green was hooked up to cylinder three.

Right was, I'm sorry, was three the misfiring one?

or no, it's a cylinder for green was on four.

Green was on four was our misfire, and then yellow should be.

There should be another event somewhere between the yellow pulses right.

So if you were to zoom out, you'll see multiple injector events.

On the yellow, there should be a green one somewhere in the middle between those right, because it's not going to.

you're not going to inject fuel into both cylinders at the same time because they're not firing at the same time, right.

Right, and so if there was nothing there, again, kind of, it goes back to what I was thinking about, like it had shut the circuit down, or maybe you see it, maybe it's there, the voltages Reading.

Now let me ask you this your trigger set up on the yellow yes, isn't that?

Yes, that's why that's why so you're always going to be focused in on the good cylinder, because your trigger is showing you that front and center.

And then whatever's happening on the green, you're going to see it, you know in the same time, and we're just picking up some residual voltage on that circuit again, maybe inside the scope, maybe something to do with the connection of the vehicle, but that that would make sense.

So my, my next test.

If I had the car right, the thing that's in front of me is zoom the scope out and see what do I have going on in between the two yellow injector events.

Yeah, so that would, that would track.

Then, like that, that makes sense to me because if, if I went down a rabbit hole because I saw a low, a low value, as far as that it didn't.

It didn't click in my head that what you're saying here, that these, these events are happening the same time and the same time in, I don't know if it'll show us we're in, we're in milliseconds here.

So the same, the same time, within a you know millisecond each other, and it's all exactly the same.

Two injectors are not going to fire at the same time.

I can only trigger off of one.

I can only trigger one trace at a time.

Snap on one.

Let me trigger off of two.

So you can then zoom out.

Well, yeah, I could, I could zoom out and look at it, but but the but.

If this test is bad and the problem is not that the that the PCM is not supplying, or the problem is not the PCM it's not supplying power to the circuit, or that the injectors drawing more current, it's that it the PCM has turned off this injector because it sees a misfire and we are getting a false test result because of some weirdness in our test equipment.

Yeah, did you try having the trigger on the bad cylinder at any point?

I did, and I did and it's the same.

I had to move the trigger really low to catch it, but it was.

It was still catching the same, the same pattern.

So I bet it was off then.

So yeah, I mean that makes the most sense.

I mean that that's not that I shouldn't say it makes the most sense.

That's the only thing that does make sense is if the PCM is turning it off because it sees the misfire and, for whatever reason, 65 volts is enough that we're bringing up the voltage on our other trace.

Yeah.

So this is a fantastic example of scope usage and where it can be such a powerful tool that can separate you and tell you things that you would never know otherwise.

But it can also leave you down a rabbit, and you down rabbit holes that you would never have gone down otherwise, and I know a lot of people that use scopes on a regular basis are aware of that.

But for somebody who is excited to buy their first Pico or their first you scope, you got to have that, you know, in the back of your mind as much as often as possible, because otherwise I've done this exact same sort of thing.

I'll find a post on on Facebook that I had I was messing around with a three eight and I was picking up inject or ignition signals from another wire, and I was.

I spent hours on it, hours and something that I would have never done had I not had that scope.

But it's like well, there it's right, there it's firing this coil twice and yeah, yeah.

So, just I, just I get a little bit of a sidebar question because you, you have a Pico, correct?

Yeah, I do, ok, so have you ever seen your Pico do something like this?

Where it's it's reading, you're reading a voltage on a channel that you're not testing on, like where you get where you get.

So we're looking at channel one and I'm also getting it's bringing up channel two for some reason when Channel one spikes.

Have you ever seen the Pico do something like that?

I mean, obviously you get a wire that's picking something up weird, but where it's where it's strictly a failure.

Yeah, this is I mean where it's strictly a failure of the tool, where the tool is reading, your equipment's reading something that doesn't exist on a wire.

I'm trying to talk my boss and to spend any money on a Pico because I don't have the cash for it.

Nothing.

Nothing comes to mind unless my setup is wrong.

That's the scenario where I could say, yes, something like that happened.

But it's when I have something set up wrong whether it be a ground lead, not you know, connected correctly, or I somehow have, you know, my leads touching and I'm not aware of it.

But that's the only thing I can really think of.

It's if you set up the test right.

I think it does a pretty accurate job of telling you what's actually going on.

So is I know.

I know you're going to have a Some some extent of an RF field around a voltage is care, or a wire that's carrying a lot of voltage like this.

Let's say you've got your two leads and you're doing this like you can't see in this picture, but slightly outside of the frame of this picture there's two piles of lead sitting there because they're each leads like four or five feet long and the scope is sitting four inches from where I'm testing would.

Yeah, I don't think that's the problem here, but could you potentially have an issue because your test leads are sitting around top of each other?

When we're talking about a voltage around 65, like this one.

Yes, and even even more so when we're talking about ignition components that are forty thousand.

But the quality of the lead changes that or reduces that significantly.

Ok, and so the Pico leads and a lot of other high quality leads.

I can't speak to snap on I've never owned a snap on scope but I know the Pico leads are shielded in a way where you don't get rid of all of it, right, and if you talk to really savvy scope users they can tell if they can look at a way for them that on a car that they were not at and they can tell you whether it was running or not, because they can see the interference from everything happening under the hood.

And there's little bits of it and you almost learn to ignore it, right, you just see the little blips in the voltage and it's picking up stuff, and so you'll get a little bit.

But the better the quality of your lead, the less you'll have that.

Now the opposite is true as well.

If you're getting really cheap leads which I've had then you then you're getting all kinds of interference into those, into those leads.

So if you're going to invest, and even if you don't have Pico, but if you're going to invest in getting into a scope, don't go with the cheapest leads possible because they're not going to be shielded to the same the same amount, so you're going to get more interference from you know, electrically speaking or RF speaking.

Under the hood is a is a very noisy place and yeah you've got your leads laying over the top of the coils and injectors and all this stuff.

You're going to be getting some, some voltage induced into those, those leads.

Yeah.

So I guess to kind of summarize what we've learned and so I, the way that my brain is wired, I process things verbally, so like as I talk through a problem, I understand it better.

I'm to kind of summarize is where where my testing procedure went wrong is I didn't notice that these spikes are exactly in sync with each other.

And I did.

I did notice, I took a picture of it, but it didn't click in my head that they shouldn't be in sync with each other Because we're testing two different cylinders.

they shouldn't, they shouldn't be synced together.

And that's kind of where I guess kind of went down a rabbit trail, because I was looking at this data going okay, there's a problem here when, if I had done maybe a little bit more testing, if I had unhooked the second lead and just used one lead and checked it, I would have seen that it was a fly line.

There would have been nothing there, yeah.

Well, you might have still, you may have still seen that one fault.

That's hard.

You'd have to test and see.

I guess there's a little.

Yeah, we won't really know, but okay, so that, okay.

So in my head I understood.

So basically what happened?

Kind of backing up fuel injector was replaced, the O-ring was left in the, in the rail or in the line that goes to it, and so there was a piece of debris that went in restricted fuel flow.

Ecm sees that as a misfire, disables the cylinder.

We have a mis, or we.

Or it sees a misfire because there's a restriction in fuel supply to the injector.

So it turns the injector off, but it doesn't set a circuit code.

It sets a misfire code and I had interpreted this test as it's still trying to fire the injector when in fact this is a failure of the tool and we're just getting bleed through voltage on the other scope trace from or between the channels.

So the problem all along is not it's ramping to a volt and that's a problem.

The problem is that the injector is off because there's a misfire which was caused by debris restricting the fuel injector.

Yeah, I can believe that, Like that makes sense in my head, that drives yep, yep for sure.

Well, I'm glad that we can make some progress on it.

That's cool.

I was like getting an answer, you know since I was a little worried cause when I I know we scheduled this really quick.

I don't know if that's typical for you, but I was, like it's fresh in my head, I want to figure it out.

But like I didn't have an answer yesterday and I didn't have enough information to come to an answer yesterday, so I'm happy to get to an answer today.

So, yeah, I think the moral of this story is, no matter how confident you are, remember that a scope is a really easy way to get down a rabbit hole and that two injectors next to each other should not fire at the same time.

Which is like common sense, like I know that, like it's not my first day on the job, Yep.

We're not used to seeing it.

You know, electrically, on a graph I mean, as some people are, obviously.

But if you haven't, you know, done that a ton, you're just looking for ejector patterns and the two things don't come together.

The only reason like that stood out to me is cause I've done like a ton of in cylinder stuff and a ton of scoping and so, like that, just that came up in my brain.

I was like, well, how come they were right on top of each other?

Yeah, it's all experienced, right, that's literally all it is, and that's a scope thing.

If you had an amp clamp, you would have caught this because you would have seen current ramp on cylinder three which is working.

You would have seen zero.

Would have never known about the one vault.

Yeah, yeah, that's what I guess I need to spend money on is an amp clamp, because that would have, oh yeah, saved us from this whole rabbit hole.

Yeah, absolutely loved my amp clamp for sure.

That's my go to for so many different things.

So, yep, that's the moral of the story Everybody go buy an amp clamp.

And I guess this is where we sit way into that ad spot for Jarhead.

I'm sure he sells something.

Also just decide now while we're here talking, I was listening to an episode.

It was your talking about your everyday carry and you referenced the amp clamp that is in your little bag.

Yeah, but you said everything in your bag was like less than 300 bucks and my amp clamp was like 400 bucks and I was just curious what amp clamp you had or what your little one that read I think, up to 100 amps is what you had.

Yeah, to be clear, this does not connect to a scope.

This has a little.

LCD display on it, so it's a.

Actually let me check the going price on Amazon here.

Cause I.

So the amp clamp that I have is great.

It'll read up to 600 amps, but it only reads down.

It is only accurate to a 10th of an amp.

So I $53 on Amazon right now for the unit T amp clamp.

Yeah, Now for this particular situation running.

It may not be fast enough to search the amperage.

Yeah, my head's off in a different world, and I'm thinking about parasitic draws now.

Okay, that's why I want it.

Cause I just need something that can read like fine amps without without spending an arm and a leg, because I still work for a living and I'm not exactly made of money, as nice as that would be yeah, no, I will say I use that thing all the time.

Are there more precise ways to do draws?

Can use a scope.

Yeah, that's fine, but I actually have two of those things.

I have another one in the van, so I'll put them on multiple cables coming out of the battery and then you can see it makes real quick work of not only is there a draw, but where's it going, like which big cable off the battery, where's the draw going?

And then I can at least find the fuse panel or the component that has the as the draw gone.

Yeah, but those things will go down to to 50 milliamps.

They'll drift if you let them sit for a while, but they're pretty.

They're accurate enough for me to get what I need.

Yeah, and usually with a parasitic draw, you're not, you're not really like.

If you're like two milliamps over, it's like you're, you're missing.

Usually it's not a two milliamp draw, that's your problem.

It's like you've got a moderate thing on or a quarter of wire and it's drawn a half an amp Like.

so usually that tiny, tiny little bit of accuracy in your, in your diagnostic equipment.

It's not super necessary, but yeah, okay.

So I total sidebar and not not at all related to what we're doing here, but yeah, no, it's all good man, Do you want to maybe send me a link or put a link in the show notes to that, to that amp.

Yeah.

Just that way I can have it, and then if anybody else, who's listening is interested in that, then they can find it as well.

I will send the link to you right now, so don't forget.

But yeah, I'll, I'll post that on Facebook group too.

Everybody should have one.

Yeah, I guess so you can.

You can crack these things open and there is an eProm chip in them, I'm told, and you can change the functions of these things.

And so when you first turn it on and my employee learned this a few months ago when we made a bad call on one when you first turn it on to any of its settings, the default is alternating current, and you have to press the blue button to get it to switch to DC, which is 99% of the measurements that I want to make is in, especially the amperage.

Not to say that you couldn't use it, but I want to measure DC amps, and so you have to press the button.

If you don't know, you have to press the button.

You're on AC and it's not a changing voltage.

Well, guess what amperage?

It's zero, and so you don't think you have anything going on.

So, but I guess you can go into the eProm and edit it.

Google, there's a bunch of stuff on it For me personally.

I'll just hit the button.

So far above my favorite, it's probably even funny.

But yeah, there's stuff out there on it so.

If you have time and the passion for that sort of stuff.

There's so many cool things you can do with electronics, and I have neither one of those two things.

I just like getting things right, and that was something that I somebody asked you at some point this is a while back in the last like 12 months, how many bad calls you'd have of things that you'd called that were wrong, and at the time I think your answer was two in the last 12 months.

And you do Diag, like every day of the week.

I mean, obviously you do programming too, and what I've shifted my mindset to is that with basically every problem on a car can be tested and you can prove generally speaking, you can prove a component failure Right, Like there is a test that can prove it.

You know, and maybe you don't have the equipment In this case I didn't have an amp clamp to prove the inductor was off but you can test to the point of finding your problem.

And I guess that's the challenge that I run into is something you said, and I think your last episode was that you get you know parts until it starts guys, that are right 80% of the time and it's like they're a start tech because they get it right 80% of the time and then and that's kind of the shop that I work in, not they're probably a little better than that, a little more Diag than just shotgunning parts at it.

But yeah, it's like pull the code, put the code on Identifix.

What's the top fix?

We'll try that.

First, you know, and the problem is that, yeah, seven right times out of 10, that works, you know.

And then I get the scope out and I'm doing this stuff and I'm like, and everybody's kind of looking at me, like what are you doing, dude?

Like what is this tool?

Guys, the scope, this is cool.

And then I go like wait out a rabbit hole.

Call about ECM but it's not an ECM, so that worked out real well for me.

Yeah, it's a tough thing because, yeah, so you make that right call, you know 80% of the time and you saved X amount of time from actually doing the Diag and so your productivity just looks awesome.

And those few that you can't figure out, you know or whatever you know, just push it down the road or whatever.

But I think even within a shop, if you know and it takes time this is an easy thing.

But you build that you know, that trust in people at the shop, that they know they can go to you and you will get the correct answer.

Now, maybe you'll get it wrong.

Right, and just for clarity for everyone listening, I've made a lot more than two bad calls in the last 12 months of my current life, but you will eventually get it right.

There's a BMW which I'm probably gonna do an episode on that I made, I called a module on it and that didn't fix it right, but I went back and I figured it out and I think that's one of the important things to remember, especially when you're doing the stuff, especially when you're just, you know, getting into the stuff.

Like scope is like okay, yeah, you're gonna make a bad call here and there, but you stuck with it, you figured it out right.

And now, next time, next time you have one of these, here's the thing next time you have something like this, like you're gonna know the ins and outs of it so so well that all of this stuff was, you know, tremendously worth the time that you spent on it.

And yeah, then, like I say so, over that time you build the trust.

People know that they can go to you, they can get you're gonna get the answer for them, and that's where the value comes from in all this stuff.

Yeah, yeah, and that's the thing is, and that's kind of where I go, especially when it comes to some of these calls where it's like I'm pretty sure, but I'm not 100% sure, and it's.

You know, what else could it be?

What else is in this circuit?

What else could what else affects this component?

What else could cause this issue?

Well, what if I'm wrong?

What do I do next if I'm wrong?

And in my head I was going through the you know, this whole process in my head while I'm you know explaining my service writer why we need a PCM and it's like, and my head was like nope, that's it, it's PCM.

Nothing else could be.

I checked everything else.

It's fine, have a nice day.

And clearly not.

So I clearly have room to grow in my skill set.

Keep an ear out for the BMW episode Cause, like I said, I told them yep, you need a DME and, by the way, I can clone it for you too.

So I went through all of that and then it was the exact same thing, and then I called my friends right, and that's the other thing is having that network.

I know I say it.

People are probably sick of hearing me saying it, but I called Fonslow and I called Justin Morgan and I went back today and you know it's like boom, bam, I got it.

Oh, how was this that?

How was I so far off?

You know, the first time around.

But it happens and the sway, the sway goes.

So I wouldn't feel, I wouldn't feel too bad about it.

Yeah, I think the real, I think the real secret or the real trick to this is is not not beating yourself up over a bad call, and and learning, going back and and working through, working through the process, like what we're doing here, going back through the process, see where, where did we go wrong, what can we do different next time, so that we don't make the same, make the same mistake.

And then and then, yeah, like networking is is a huge thing.

I I really needed, I need to meet more people that do like advanced diet, because I only knew one guy and it was like an old boss and we were on good terms, but what I learned is that my diet skill like past, his like two years ago, and and so it's like there's there's not a lot of.

I don't.

Sean, you're the only guy I know.

And I don't even really I mean I.

I listened to your podcast but, like there's nobody else that I know that I can talk through this problem with and go.

What did I do wrong?

Cause I just I'm sure I didn't know that things like vision and AST and all these things existed up until like six months ago, cause I've been living under a rock, yeah, I mean, no, that's the majority of technicians out there, myself included.

If I go back 10 years, I had no clue, not a no idea any of that existed out there and the the groups of people that are out there.

So I'll send you some, some invites to some Facebook groups that you can get into and that's a good place to start.

Like, you can see, you know people talking about stuff.

You can post stuff like hey, what do you think of this injector waveform?

And that that's where it starts.

And then you go to the events, you meet the people and then that's when you really can you got a phone number to call right.

That's the thing.

It's like no one, no one who to call and no one, no one.

Your guy, that it's.

It's just funny because, like I'm that guy for so many texts that I that I know it in the area and even just in other areas that I've worked in, it's like I I probably average like two or three phone calls a month.

Hey, do I got this problem with a power struggle?

I can't figure it out.

It's like it's great, but the problem is everybody's calling me.

I have nobody else to call, so I need to spend some time building that network up myself, yup.

Well, I was.

I was talking to somebody the other day who knew me from way back when, you know, I've been fixing cars since I started as right out of high school or in high school, right, and I was telling them about what I'm doing now and all of the crazy smart people that I've met and that I'm like, I'm like a kindergartner when I, you know, I'm in some of these groups or I feel like that, and he's like, he's like you, he's like you always fixed everything, blah, blah, blah.

And I was like, no, you don't understand.

Like you think you're good at this stuff.

And then you meet these other people that are like, holy shit, like I'm, I'm in, they're in a different world, they're a different type of person, their brain functions completely differently than me and I just hope to glean a little bit of information off of them.

It's like you know, you're, you're the high school hockey star, right, and you're, you're dominating, scoring five goals a night.

Well then, you try to go play in the NHL and you're a fourth liner, you know that's.

That's like the how I feel about it sometimes, but I do like it, like I want to be surrounded by as many people that are really smart, really good at this as possible and, like I said, just sort of uh, yeah, there's something to be said if you're the smartest person in the room, you're in the wrong room.

Yes, I agree, surround yourself.

People that are smarter than you, and it's going to make you smarter, and that's that's yeah that's, that's really the trick.

And just in continuing education and always learning, and when guys, guys get settled into a groove and they can turn out production especially when they're flat rate and you're making money, it's it's really easy to just get stuck in that groove.

But it's like I don't want to be stuck in that groove, I want to, I want to understand what I'm doing and I want to be the best at at what I do.

And and I'm, I'm like I would tell you that I'm pretty good at what I do.

And then I, I, I listen to people like you and Fonzlo and some of the other guys, and it's like I'm, I'm just like a little kid, like I don't know, am I even allowed to touch tools?

Like you can hold the flashlight, okay, yeah.

Yeah, exactly, exactly.

So, anyways, oh man, well, thanks for sharing that with us.

Uh, that I actually.

I really enjoyed that.

That was cool yeah.

I think we both.

I think we.

Well, I don't know if you learned anything.

I learned something, All right, that's going to do it for today's episode.

Thank you, andrew, for joining me.

Uh, that was great.

Hopefully everybody listening enjoyed that as well, and uh learned something from that.

I thought that was uh really good to point out.

You know this, this thing about lap scopes, where I definitely I need I use them all the time.

I need them for my job, but you have to remember not to pick the fly shit out of the pepper, right, uh?

And that can happen.

It happens to me all the time.

So, anyways, uh, thank you again, andrew.

Thank you everybody listening, but with that all out of the way, let's get out there, start fixing the world, one card at a time.

206: Scope Rabbit Holes With Andrew Rogue

Chevrolet Malibu

Ford Super

About this episode

Original notes