0:00
/
0:00
217: Cam And Crank Reluctor Diagnosis
217: Cam And Crank Reluctor Diagnosis
0:00
0:00
0:00
0:00
About this episode
Two complex diagnostic cases involving cam and crankshaft reluctor sensors highlight the challenges of interpreting circuit codes. A 2016 Mazda CX-9 with a no-start issue revealed a damaged camshaft reluctor wheel missing most teeth, while a 2014 Infiniti QX-80 showed a faulty crankshaft reluctor on the flex plate after timing chain repairs. Both cases emphasize the importance of using oscilloscope waveforms to verify sensor signals and patterns rather than relying solely on code definitions. The episode also discusses how some vehicles run on cam sensors alone and the critical role of timing and sensor integrity in engine management.
Topics:
camshaft reluctor diagnosis
crankshaft reluctor diagnosis
oscilloscope use
sensor waveform analysis
engine timing issues
diagnostic trouble codes
mazda cx-9
infiniti qx-80
timing chain problems
automotive diagnostics
Today on the show I share 2 case studies on vehicles I had back to back with very similar problems. First a 2016 Mazda CX-9 and then a 2014 Infiniti QX80. The Mazda is a no start and the Infiniti starts, but with several issues.
Website- https://autodiagpodcast.com/
Facebook Group- https://www.facebook.com/groups/223994012068320/
Email- [email protected]
Please make sure to check out our sponsors!
Automotive Seminars- https://automotiveseminars.com/
Jarhead Diagnostics- https://www.jarheaddiag.com/ USE CODE- DIAGPODCAST FOR 10% OFF
L1 Automotive Training- https://www.l1training.com/
Autorescue tools- https://autorescuetools.com/
Filter:
|
Technical
Too Afraid to Ask
Car
Mazda Cx9
"But either way, interesting enough, even if it was just one. So the two vehicles that we're going to talk about, one is the 2016 Mazda CX-9, and the other one is the 2014 Infiniti QX-80. So I'll do it in chronological order."
Car
Infiniti QX80
"But either way, interesting enough, even if it was just one. So the two vehicles that we're going to talk about, one is the 2016 Mazda CX-9, and the other one is the 2014 Infiniti QX-80. So I'll do it in chronological order."
Select text to request an explanation
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 podcast is brought to you by Jarhead Diagnostics.
Jarhead Diagnostics manufactures in-house diagnostic equipment and storage solutions, as well as distributes for companies like Pico, ats and Topdion.
One of my favorite tools that I have bought from Brandon and Jarhead Diag is the case for the Uscope.
If you don't have a Uscope, you probably should, but if you have one, you got to get.
One of these 3D printed cases has a magnet on it, has a full-size BNC lead that you can connect to and it gets rid of the weak point of that scope, which is the mini BNC connection, which is pretty fragile.
This case makes this thing nice and secure and makes it even better tool than it was.
So check out jarheaddiagnosticscom.
The link is in the show notes.
Hey, for listeners of the show, if you want to discount on Jarhead Diagnostic products, use discount code DIAG Podcast, that's D-I-A-G-P-O-D-C-A-S-T DIAG Podcast for 10% off purchases from jarheaddiagcom.
I am happy to have Automotive Seminars as a sponsor for the show.
Now, if you're not familiar, automotive Seminars is a diagnostic technician training company.
They've got a website that they'll be a link to in the show notes, and what they offer is top-notch training to technicians like us in the field.
I've been taking their training courses for years and have got a ton of benefit out of it.
They've got top-notch instructors John Thornton, scott Shotten, scott Manna and every other month they've got a two-night course that you can sign up for, join in, ask questions and afterwards you've paid for the course.
You can access a recorded version whenever you want.
You can re-watch the class two years later in case you wanted some details on it, and that is a fantastic feature.
So make sure to check out the website to see what courses they have available and what's coming up in the future.
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 Today on the show.
I'm going to talk about a couple of vehicles that I had the other day literally back-to-back stops for diagnostics on these vehicles and ended up being very similar problems which, when I got to the second one, I was like no kidding, it's not the same car, not exactly the same problem, but very closely related and I thought it was interesting.
Just the one, but that I had two back-to-back.
Sometimes that just happens.
You get stuff in waves for whatever reason.
I mean, obviously, if it's a common failure part, that makes sense.
But sometimes it's not even that, it's just you end up with the same problem back-to-back or over and over, and I've experienced that a number of times throughout my time in the industry and I'm not exactly sure why, but it does happen and this is an example.
But either way, interesting enough, even if it was just one.
So the two vehicles that we're going to talk about, one is the 2016 Mazda CX-9, and the other one is the 2014 Infiniti QX-80.
So I'll do it in chronological order.
The first one was the CX-9.
Again, that's a 2016.
The shop had just installed a brand new engine and this is a 2.5-liter
four-cylinder engine in this thing.
Again, shop had just put a brand new one in, said it doesn't start, and we went through it.
We're not exactly sure why it does not start Now.
Had they really scanned this thing and looked at the code, might have pointed them in the right direction.
I mean, I know what it would have because that's what it did for me, but there's a number of shops that I service that are very busy and when they run into an issue with something they're just going to call me out because they know it's more efficient to get to the solution and they can keep their texts on other, more profitable work.
So that's kind of where this one was.
But, anyways, hook up to it.
And there's one code in the engine computer and that is a P0365.
Now the definition for this code and something I really want to touch on here is the exhaust cam sensor circuit.
All right, it says that on the scan tool.
It says in the description of the code exhaust cam sensor circuit.
Now it's really important and I find this to be true a lot with speed and position sensors like camshaft, crankshaft, even maybe wheel speed sensors but cam and crank are the big ones that we deal with, related to an engine that you don't take the code necessarily at face value, based off of what the name of the code says in the scan tool, right, or the name of the code in service information.
And when it says circuit, make sure to take the time to understand.
Is this an actual circuit code, meaning that it's seeing an open or short or no voltage where it expects to see voltage.
Do we have an actual physical circuit electrical problem or with a speed and position sensor?
Is it the case where the pattern that the computer is expecting to see is either not there or it's not there in the right amount or it's not there at the right time that the computer expects?
And this is the case for a lot of cam and crank sensor circuit codes and a lot of the time if you look into the code information, you actually read service information.
That's the key here.
Of course, like always, there are multiple things that can set this circuit code.
They give it one definition, but there's a bunch of different things.
It could be an actual circuit problem.
That's definitely possible.
Because if there was a circuit problem let's say the signal wire this is a three wire hall effects sensor.
There's a 12 volt feed, a sensor ground and a signal wire that goes to the engine computer.
I mean, if any of those wires were open, this could definitely cause this code, because there would be no signal getting back to the ECM or coming out of the sensor at all and you could get this circuit code.
But if you read down the list of things that can cause this code.
It also says that there are not enough pulses within X amount of time of revolution of the crankshaft.
And again, this is an exhaust cam sensor and the computer is gonna be referencing the crankshaft sensor and looking at the cam shaft to determine okay, here's where every cylinder is at within the four stroke cycle.
Now I fire the coil here, I fire the injector here, based off of those signals, and cam shaft sensors of course, are going to determine for the ECM exactly where this thing is in is four stroke cycle.
We can only determine so much off of the crankshaft.
We know the piston's up, but is it up on compression or up on exhaust?
We don't know unless we reference the cam sensors.
So that's what it's using.
But again, going back to the code, one of the things that can set the code is not enough pulses within a given amount of time or the pulses are too far off from where they're expected to be right.
There's a pattern from the teeth on the re-electro-wheel of the cam shaft and that pattern should match up to the crankshaft pattern.
Okay, this engine timing, that's all it's looking at.
So, again, electrical pulses and inferring engine timing and if this is too far off or not the right amount or none at all.
You can get this circuit code, okay.
No, that means something to me, because now I have to determine what's actually happening on the signal wire.
And of course I mean I guess if you had a circuit code you could probably get to that conclusion as well.
But I like to know all the different possibilities that could set this circuit code right.
I'm not solely just dialed in on an open or short on this wire.
It could be for sure, but it could also be a timing issue.
It could also be something wrong with the sensor or the re-electro-wheel.
Okay.
So what am I gonna do?
I'm gonna scope the sensor.
That's step number one here, and it's easy to get to.
It's on the backside of the cylinder head, of course, on the exhaust cam, and I got a U-scope plug into the signal wire.
Let's crank this thing over and see what happens.
And just for reference, this thing doesn't even pop, it just cranks, that's it Sets this code every single time.
So I'm looking at it and it does actually have a pulse as the engines rotating, and it looks to be just one tooth over and over and over again, or the same pulse Over and over and over again.
That's the way I saw it when I first saw this.
I'm like, okay, well, it is making a signal.
Now I'm measuring at the sensor.
I would probably need to measure at the engine computer to make sure that it's getting all the way back, but it is making a signal when it's rotating, so something's happening.
It's not you know, it's definitely not an open circuit on the power of the ground at the sensor.
Again, I could check the signal wire back to the ECM, but something's happening there.
But what I want to do is I want to compare what I'm seeing there to a known good pattern, and that might lead me to Tying into the crank sensor.
I didn't do this yet because I was just using my u-scope one channel and I'd have to get out the pico if I want to do a comparison, which I might have to.
Maybe the timing's out on this thing.
It's brand new engine but that doesn't mean that it was timed correctly.
So that known good is gonna be useful to me for a couple steps.
I might as well get that now and then at least compare the pattern that I'm seeing to the known good.
And actually One thing I should mention here when I was going through the service information.
There was a actual waveform pattern in the service information For Mazda and it showed this camshaft sensor what it should look like on a scope, and it did look very different than mine as far as the amount of pulses that it had compared to what I was seeing, and that's kind of another reason why I'm like okay, I want to verify that a known good captured off of of engine like this is either the same or different than mine.
I Views the waveforms in service information before and a lot of Asian makes have been doing that for a Decent period of time where they'll include a known good.
I can say that it's not always 100% accurate.
There have been examples where I've seen where it's not the exact pattern that you're gonna see on the car, but there are times where it is very, very close or to the same as what you would expect to see on the car as far as when the pulses are in reference to one another.
Now, they generally don't give you like a full cam and crank waveform, but they'll give you the individual picture of here's what it should look like.
So I'm gonna go on to some of the resources that I have, and there's a number of them out there where you can Find someone else who's captured a known good cam crank waveform from said vehicle.
And I was able to find more than a couple and Pull them up and they all look identical to the one I saw in service information when, if you can imagine, it actually has like a double pulse.
So there'll be like two, two, one, one, two, two, one one, and I didn't have that at all.
Like I said, I have a repeating just one little pulse over and over and over again as the sync cranks.
And the next thing.
I did it because I had the known good up with all Three sensors.
So there was intake, exhaust and crank.
I just moved my lead over to the intake Cam shaft just to see does this match the known goods that I'm seeing here?
And it did.
It had the double Tooth thing and then one, two and the intake in the exhaust.
On these, the patterns Themselves are very, very similar.
Now they're not lined up exactly the same in reference to one another or the crank, but the actual pattern, the Tooth arrangement on the re-luxur, is very similar between the two.
So if you're scoping these things it just one at a time they should look very similar to one another and they didn't.
Again, the exhaust is only like one tooth.
So I mean, I think I'm on to something here.
There's definitely something wrong with what's going on.
And my first thought is we got a look at the re-luxur on this thing to see why am I only getting one reading?
So let's pull the exhaust cam sensor out and We'll put a bar scope down in there and see what's going on.
So I pull the thing out and immediately see what's going on.
There's damage to the end of the sensor and there's actually a metal tooth that's stuck to the magnet at the end of this sensor.
As I pull it out I'm like, well, that's not good, this is a brand new motor.
So we stick the bar scope down into the hole and rotated the engine by hand and Turned out there was only one tooth Out of the six that should have been on this, a camshaft, and that was the only one that was left.
And Something, somehow or another whether it was on assembly or installation, I don't know.
Something knocked off all of the teeth on this thing except for one, and there was a Vacuum pump that was bolted to the end of this camshaft.
And I was saying to the shop owner I'm like maybe something happened there, maybe it happened on assembly, I have no idea.
You guys are gonna have to take it apart, obviously, find all these teeth, because this is a brand new motor and you don't want these little teeth that are smaller than your fingernail Rattling around in a brand new engine.
That's obviously going to be very bad, but you're gonna have to replace the camshaft as well, because this tone wheel is pressed onto the back of this thing.
So Unfortunate news for them, but they got to go back in this thing.
Take it apart, try to find the pieces, if they can, and Find out what damaged it to.
You know, is there a bolt lane in there or something?
I'm not sure?
I guess for me.
I kind of like that.
That's not my part of the job.
I just tell him what's wrong and pay me and I'm out.
So the perks of the mobile gig On to the next one.
This was a 2014 infinity Qx 80 with a 5.6
liter v8.
Now, I'd actually been to this vehicle for diagnostic Two months prior.
I think it was in either June or July of this same year, and now we're in September and they had originally called me in for a really weird noise that this engine was making when it was running, and I don't usually do noise diagnostics, but they said it's definitely coming from the engine.
We're just not really sure where to go with this.
So I did, and what I ended up finding was it was the Timing chain that was making a noise, and it wasn't your typical like rattling timing chain is more of like a Droning or a worrying noise.
And what I ended up finding was one of the guides on the passenger side of the engine had broken and it had kind of wedged the timing chain up Against another component.
And the way I was able to see this was I pulled the cam sensor on the top and I put my Bore scope down in through that hole and I was able to actually see that the guide was broken on this thing.
So they needed a timing job.
That's what I told them.
I think you got a you know quote on timing chains and all that good stuff and go for it.
So they did that.
I Took them a really long time.
I don't know if it was parts or the procedure itself.
I never really heard back from it until Just now in September and they said hey, we did the timing on this thing and now we have a P0 335.
We can get this thing to start, but it surges like crazy, it doesn't run right and of course we have this code.
We've been through everything and we recognize that the P0 335 Was for the crankshaft sensor.
So we replaced it with a new one from Nissan Infinity and they didn't change anything.
We still have the same code and the same symptoms.
Can you come out and look at this thing?
Okay, cool.
So I Come out and of course I've got on my mind that they just worked on this thing.
This did not have this code when I came to look at it, way back in June or July, so the problem is most likely man-made.
But still figure out what's going on.
I scan it and I do have the code P0 335.
Again, same thing.
On this one it says CKP sensor circuit.
Okay, so it's saying that there is a circuit problem.
But if you just go over and, like I, have the service information open and you go over one section here, it gives you three possibilities for this code to set.
This is crankshaft position sensor signal is not detected by the ECM during the first few seconds of engine cranking.
Okay, that's one.
Number two the proper pulse signal from the crankshaft position sensor is not sent to the ECM while the engine is running.
Okay, so what does that mean?
That mean could be a pattern, but not the right pattern, and that's going to set a circuit code.
Or this is third one the crankshaft position sensor signal is not in the normal pattern during engine running.
So does that mean timing could cause this code?
It's possible, maybe, right?
So we have different possibilities.
And again, I'm just stressing the fact that just because you see circuit code on the scan tool doesn't mean that it necessarily is the circuit itself.
It could be, but it could be other things as well.
And as long as you have that in the back of your mind and then you say, okay, well, now I need to go determine Exactly what's going on with it rather than just saying, yeah, it's a circuit problem, it's going to help you out quite a bit, or at least having in your mind that there are multiple possibilities that could cause this type of code and you need to do a little bit more digging in order to figure out exactly what's causing it.
Right, that's our job as technicians is let's figure out what.
What's actually causing this code through testing.
Okay, now again, in this case the scope is the answer.
Right, the scope is not always the answer, and I pulled out my pico for this one because my, my thought is that you know, they just did the timing job.
It's very possible the timing's off and I'm probably gonna be doing some sort of comparison Between the cam and crank sensors just to determine did they do the timing right?
It's my, it's my first thought.
Now, something I should note here when I was in the car and I was scanning it and I started this thing up, I noticed something, and this is true of Nissan's and some other vehicles as well, but I've definitely seen it on Nissan's Nissan's will run the engine without a crankshaft signal.
You don't need it at all.
You can unplug the crankshaft sensor and you can actually run the engine.
Now a couple things.
You'll have an extended crank.
It will crank for a longer period of time before it starts and when it starts it's gonna kind of be all over the place as far as surgery goes.
It's not a smooth running engine, but it will run off of the cam sensors.
It's got enough detail that it can figure out the position of the engine.
Okay, and there's other makes and models like that when they'll run just off the cam sensors, and this wasn't always true.
You go back and then you know, I don't know, 15 years or so, maybe more, if the crank sensor was dead you were not going to start that engine.
But a lot of vehicles now.
You don't necessarily need it and the tough part is you don't always know like some cars the crank sensors definitely gonna kill that engine all the time, and then others, like this, it's not the case.
Now, one thing you can do here to kind of prove out you know, obviously you have the code, but On these Nissan's you can try clearing the code while the engine is running right.
So you do the extended crank, you get it started, go into the ECM, clear that P0335 and if the engine stalls you know 100% that there is definitely something up with the crank sensor, the pattern that the engine computer is receiving, because what it's doing is it's looking for it on startup, and that's your extended crank.
It's like okay, where is everything here?
I don't understand the crank sensor signals Not right.
Okay, I'm gonna go off of my cam sensors and then start and run and with this code present, it's now in the default state of just using cam sensors until you try to start it again or you clear the code.
When you clear the code, the ECM goes back to trying to use the crank sensor and if there's an issue, which there is in this one, it can't and then the engine stalls.
Okay, so it's just a kind of a confirmation, before I even get out of the driver seat, that yeah, we definitely have something up with the crankshaft pattern.
Now I will say, minus the surging, this thing was actually running halfway decent.
So if the timing is off, I didn't think that it was off extremely Far amount, but again, I'm not.
I'm not sure I'm gonna go after the crankshaft sensor here.
So Get this thing in the air.
And it was already racked for me, which is nice.
The crankshaft sensor is actually located on the passenger lower portion of the bell housing of the transmission and it reads off of teeth that are on the drive plate between the the engine and the transmission.
So I tie into the sensor there, find my signal wire, and what I did here was I have my Pico out again, because on this one I'm almost assuming that I'm gonna need to do a multi-channel pattern comparison between the crank, the cam and crank the cam sensor on the passenger side up on the top of the engine is really easy to get to, and so what I'm thinking here is like I'm just gonna get a cam and a crank
and If I want to do a full comparison of Timing I'll need to get the other cam sensor, but it was kind of buried on this one.
And here's my thought process behind this, and I'm sharing this because this is kind of like an efficiency move for me as I'm doing mobile, like how can I get to the conclusion as quickly as possible?
I Know that there's an issue with the crankshaft pattern, some holler or another.
I haven't even seen it on the scope yet, and To do a real accurate cam crank analysis I would need both camshafts and the crank.
But Since I can assume that the issue lies with whatever's going on with the crank sensor, I should be able to compare it to just one camshaft and still get my answer Right.
I should still be.
If it's out of time, I should be able to see that, using the one cam sensor on the one side of the engine and the crank sensor, compare it to a known good.
And Because the crank seems to be my Fault.
Based on what I'm seeing, I should see that it's out of sync with the other camshaft that I'm using and there'll be a Third or a second camshaft that I don't have in the pattern that I'll see in the known good, but I may not necessarily need it.
So I'm just trying to save myself a few minutes here of testing, just to get an answer.
So I do this.
I would get up, go to start this thing, and I do have a crank pattern.
I do have a cam pattern as well, but the crank pattern looks very strange, and what I mean by that is when you look at crankshaft pattern on most vehicles you'll see a repeating pattern.
Of course that's any speed and position sensor with a Gap in the teeth.
Every so often, right a set amount of teeth, you'll have a gap.
It's a sink mark for the computer to know where it is in rotation, and then you'll see the same pattern again, or maybe you'll have two different sections, but there'll be a, basically a spot where there are no pulses, the missing tooth, if you will, for the crankshaft Reluctor, and that will repeat itself over and over again and some Patterns will be a little different where you'll have.
You know, maybe there's two different sections and they have different amounts of teeth in them or or something like that.
A lot of them are the 58 tooth.
This one is not that.
But you see kind of a repeatable pattern of a section of teeth and then a gap, a section of teeth in a gap, and that's what I'm used to seeing on most crank sensors.
And this one had a good section of teeth but then it seemed to have missing teeth every so often in the second group and then we'd go back and have a good section and then again there would be missing teeth in the second group of pulses.
And it didn't seem right to me because where the teeth were missing it was just sort of In the middle of the pattern and it didn't.
It didn't seem right based off of what I'm used to seeing with crank sensors.
You know I don't know this pattern by heart, by any means, and I'm gonna look up a known good, but something didn't seem right with that pattern.
Now what I did notice that it was repeatable, right where the teeth were missing where I think they should have been.
It was the same every single time the engine came around and this is off the cranks crank sensor which is on the back side of the engine right.
So I get my known good, which was easy enough to find.
I'm just looking at the crank signal on this one.
I don't even really care about the correlation at this point.
I mean I can double check that just to make sure that I am on, because they did do timing.
But what I'm most interested in this point is what does the pattern look like and doesn't match mine or not?
And I find one and it does not match mine, just like I was thinking where there are missing teeth in my pattern, missing pulses.
There are not missing pulses in the known good and I checked a couple of them just to make sure and I'm like, okay, I know what I need to do now.
And I just been on the other job where I had a damaged reluctance.
I'm like, oh, what are the odds?
So let's pull this sensor out.
Super easy to get to one ten millimeter Bolt.
I got a yank out of there.
And then I rotate the engine around because when I first looked up in there I saw a couple teeth.
I was like those look fine.
But there were some that were fine on the pattern as I rotated this around, number one, I saw some clear damage on the actual torque converter body, like it looked like metal had scraped against it recently, like you can tell that fresh Scrape into the metal from something else metallic.
And I rotate this thing around and there were probably three or four of these teeth that had clearly been hit by something, damaged and bent, and that was what I was seeing within the pattern.
And so this was feeding into the computer and it had no idea what was going on with the crank pattern, because all of a sudden we're just missing teeth where we're supposed to have them.
Computers like now.
I can't use this.
I don't you know.
I'm trying to do the math here on where the engine is and this isn't making any sense.
I'm gonna give up.
Set this code, go off the cam sensors.
Now I asked the guy.
I'm like hey, did you guys do anything on the backside of this motor?
Because all the timing is up front.
I was like he didn't yank the motor out of this thing.
They're like no, no, we didn't do that and the tech who worked on it wasn't there when I was there, so there may have been something that he did back there.
I was thinking when did he pull the starter out for some reason and drop a bolt down in there?
The engine and the trans are sealed together pretty good.
There's no Inspection plate that you can get in there with, so something's probably laying at the bottom between the two.
I told him you know, you guys will have to take it apart now because it's gonna need a flex plate, because that tone wheel is part of the flex plate, and so you got to separate the engine and trans and replace this thing, which sucks.
The guy was not happy to hear that.
You know, they've had this thing for a couple months and whoo, that's, that's not a fun thing to hear.
But the damage was caused and that was not there before.
So somewhere along in the repair that was caused by them.
So they're gonna have to figure that out and fix it, which, hey, again, that's, that's tough.
That's automotive world.
Man, you can't.
You can't make mistakes like that cuz it's gonna cost you.
But anyways, I thought both those were interesting.
You know the the pattern that the Engine computers are using, where it's counting the pulses and referencing them to the other pulses from the other sensors and then Makes your engine run, fires all the coils and the injectors at the right time.
If that's screwed up for any reason and there can be a number of them Well it's gonna throw everything out the window and a lot of cases these things won't run or they'll run, but in a default state.
But on speed position sensors, man scopes are the answer.
They're not always the answer right, I don't always pull out my scope, I'm usually going with the u-scope, but sometimes it's the pico, but they are the quickest route to a solution when it comes to these speed and position sensors.
So you got to have them, got to understand them.
It makes life a lot easier.
But that's all I've got for you today.
Thank you so much for listening to this show.
I really appreciate it.
With that out of the way, let's get out there and start fixing the world, one card at a time.
Request an explanation for:
2 cars
2 cars featured
Request an Explanation
Heard something you'd like explained? We'll add it to this episode.
Sign in to request explanations for terms you heard.
Want to learn more?
Browse our glossary for plain-English explanations of automotive terms, jargon, and concepts.
Help improve this episode
See something that's not quite right? Our annotations are AI-generated and can sometimes miss the mark. Click the flag icon on any annotation to suggest a correction.
Report incorrect info
Suggest better explanations
Flag missing cars