332: Parasitic Draws Are Just Network Problems In Disguise

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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 this week's episode.

Just me on the show this week, and I'm going to share some thoughts from doing

mobile diagnostics over the past couple of weeks.

Lots of diet requests lately, I guess always.

It's in high demand.

If you can figure this stuff out, there's people that are willing to pay you to

figure it out for sure.

It's not always easy.

Sometimes kicks are but, but I still enjoy it.

And I'm trying to share on the show as often as I can just some tips that might

change your mindset on stuff a little bit when you're jumping into diagnostics.

And as you've probably heard on this show plenty of times before,

I've talked about parasitic draws that is challenging diagnostic can be

time consuming, but very common.

And it's something that the customer 100% wants to get fixed.

Otherwise the battery's just going to keep dying unless they put one of those

disconnects in, which some people do.

That's their fix for it, but it's not ideal.

So we want to fix the drain on the battery.

Obviously many of you have dealt with them.

You've heard a lot of the case studies.

Maybe you've even been to my class.

I have a class on parasitic draws because I did so many of them for shops.

I got a process down pretty well and I go through that process.

I go through the details, the specifics, some case studies.

And I've also shared some case studies on the show here with you as well for

the ones that I've found been maybe a little bit more interesting or,

you know, challenging in one way or another.

And there's a lot that goes into it, but I want to go off of one aspect

today because it is one that when I talk to technicians out in the field

that, you know, they're calling us in for these parasitic draws,

there's not a ton of people who grasp this idea.

Now I'm sure plenty do.

And if you're listening to this show and you've heard case studies from me

before or you took my class, you do as well, but maybe not.

Maybe you're new to this.

Maybe you haven't done a whole lot of parasitic draws just yet.

Or you're doing them and you're maybe just still in the older

method of tracking down that draw.

But as vehicles and technology and the platforms evolve, these

problems evolve with them and we need to be ready to pivot.

Now you could jump forward to like really new vehicles and say, well,

hey, our parasitic draws are going to be a thing in the future

because there are like battery management systems on some vehicles

that will actually like shut things down in order to prevent a parasitic draw.

It's like a management system for the electrical draw on a battery.

But not everything has that.

And I mean, even in that case, you still might have to figure out

what component is staying awake, is drawing current when it's not supposed to.

To be honest, I don't have a ton of experience with those systems yet.

I've just seen a few vehicles with codes indicating that, hey, there was

excessive draw on the battery after shutdown and whatever modules in charge

of that is actually like shutting things off.

I'll be telling us, I need to read up on it a little bit more just to see the details

and how it's done.

Of course, it's going to depend on vehicle platform.

But anyways, the cars I'm dealing with, they're killing the battery

and nothing is stopping it.

But when we're getting into these vehicles, parasitic draws,

there is one thing that I'd like everybody to think about on a modern vehicle.

What do I mean by modern vehicle?

I don't know, built within the last 10 years.

You could probably go back further than that, depending on the platform and the vehicle.

But vehicles within 2015, 16 to now, one thing that they're going to have in

common, just about everything, is there is a communications network.

And my point here that I'm going to try to drive home today is that on modern

vehicles, a lot of parasitic draws, not all of them, still possible to have

your regular parasitic draw.

You're going to go through the traditional format to find the source.

But that a lot of parasitic draws on vehicles now today are really just a

network challenge in disguise or a network problem in disguise.

Now, I'm not saying necessarily that a problem with the physical network is

going to cause a draw on the battery.

But the way that we find the problem ends up being the same way that

we find a problem with a communications network.

So I'll explain that and maybe you already see where this is going.

But I want to get this across to you because it changes my process on these.

When I consider that, that, hey, the thing that is drawing on this battery,

on this particular vehicle, I'm going to end up looking at the vehicle

network to see which network or which module is staying awake, which is

causing the battery drain.

I want to identify that early on and it completely shifts my diagnostics, right?

I go from using an amp clamp or using voltage drop or pulling fuses, whatever

your method is exactly to determine where the current is going.

It shifts to looking at a network and breaking it down into subsections to

find the module that's staying awake and then trying to figure out is that

the module or something else keeping it awake.

But if we can quickly identify on these vehicles that a network is awake,

we can almost like disregard the amp clamp for a while, right?

So traditionally speaking, in a parasitic draw diagnostic, we're

starting with how much current is leaving the battery after the

shutdown period has occurred, right?

Whatever that is, right?

Is it five minutes, 10 minutes, 40 minutes, whatever it is.

Okay, it depends on the size of your draw as well.

There's, I'm not going to go into all of that, but when the vehicle is

supposed to be asleep and at 50 milliamps, it's at two amps.

Okay, so we've identified that there is an excessive amount of

current coming out of the battery when it's not supposed to.

Now, my next question when I'm doing a parasitic draw is where is

that current going off of the battery?

Now, generally speaking, if you look at your battery, you've got

cables on the negative and the positive side.

I mean, I guess that's true for all batteries, but they're going

to go to different locations, right?

Maybe you only have one ground cable that goes to either the

engine block or the chassis.

Maybe there's a couple of them.

Um, but on the power side, a lot of the time, you know,

you'll have one that goes to starter alternator, one that

goes to the under hood fuse block, one that goes to the

under dash fuse block, right?

And you can use your amp clamp and you can use your amp clamp

and you can put it around the different cables to see, oh, okay.

Right.

I have two amps of draw total, right?

I've measured that at the, at the battery and all two amps

or almost all of the two amps go to the under dash fuse box,

right?

And then I'm going to go there and maybe I'll start doing

some voltage drop testing across fuses.

That's possibility.

I may still do that.

Very possible.

Right.

But if the thing that I've changed about my process in doing

this is before I'm even pulling out a amp pound or a volt meter

to do voltage drop across fuses, right?

I'm still, I was still going to use the amp clamp and verify

how much current is coming out of that battery when it's supposed

to be asleep.

Yeah.

But once I've identified that, hey, a draw is actually

happening, and especially if this is somewhere between one

and three amps, somewhere in that neighborhood of total

current draw on the battery, this could be something else.

But I am going immediately to the vehicle network or networks

and see if I have can bus or network activity at that time.

And this usually ends up being can bus and it generally ends

up being some sort of interior body can, but not always.

There are powertrain cans and other can networks that can

be awake as well.

But I'm going to look at how is this vehicle network constructed?

Can I access all of them through the DLC?

Do I have to go to a module?

How much work is it to access it?

How many networks do I have?

But I'm going to actually skip ahead in my diagnostic process.

And I'm going to check that.

And I've even started doing this while I'm waiting for the

vehicle to go to sleep, right?

Is that the 20 minute wait period?

Again, depends on the size of the draw.

If you draw four amps, you don't have to wait 40 minutes.

I can guarantee you that if you draw 250 milliamps, maybe you do.

So determine what is the actual size of draw that you're dealing with?

If it stays high at four amps for 10 minutes, we'll just find that.

You don't have to wait another 30.

But while I'm waiting for it to go to sleep, I will figure out

the network structure, how to tie in and I will get my scope

hooked up to the network.

Whether that be a use scope or a Pico, sometimes having the multiple

channels here is helpful and I'll touch base on that as well.

But I want to see network activity.

And maybe during that wait shutdown period where the vehicle

hasn't fully gone to sleep yet, there is still network activity

and that's normal.

But here's the deal.

When there's network activity on a can bus, interior can, body can,

whatever it might be, and that extends past that time where

the vehicle should be asleep.

That is now the problem that you're going to track.

OK, what I'm getting at there is if you start testing fuses, which you can,

you can figure out, OK, which fuse has the voltage drop?

Where's the current going?

What circuits and it's a can bus that is awake in multiple modules

that are talking when they're not supposed to.

You're going to find multiple fuses with current going through them.

OK, and then this gets really confusing.

Like, oh, I have to pull out eight different fuses to get the draw

down to an acceptable amount.

Where do I go with that?

Right.

And I've been in that situation.

I'm sure most of us have been in that situation looking for a draw.

We're just like, well, let's draw here.

Let's draw here.

How do I determine which path to go on?

A lot of times with that ends up being is a network that's awake.

So where I'm going with this is I just want to eliminate that

right off the bat, maybe concurrently while I'm checking

other things or waiting for it to go to sleep.

Like I mentioned, I'm getting my scope hooked up or at least getting

access to the network and I'm skipping ahead past all the fuse

testing because here's the deal.

If I have determined that I have waited the acceptable amount of time

for the vehicle to go to sleep, OK, and I've determined that there

is excessive draw on the battery and I've got my scope hooked up

to a network on the vehicle and I see activity.

I don't really care about my amp clamp anymore.

At that point, I just need to figure out who is talking,

who is keeping the network awake, right?

If that traffic stays on the network indefinitely,

that's now the thing that I am following.

And this is where I'm saying this now becomes a network

diagnostic, not so much a parasitic draw.

Once I find the source, the module who is talking,

then I'll disable it, you know, I'll unplug it, whatever I have to do.

And then I'll check my amp clamp and make sure it goes to sleep.

But I did this recently on a Lincoln.

I didn't even pull out the amp out on this one.

I saw, OK, we had somewhere in the neighborhood of two and a half,

three amps, somewhere in there.

And I immediately went to the network.

Now, on this Lincoln, you can get to two networks of the DLC,

the other two at the back of the gateway.

And so there's a little bit of work to access the network,

but you can get creative and you can find components

to where it's easier to tie in.

But it didn't matter because all of the networks were awake.

OK, there was three high speeds and a medium.

Everybody was talking indefinitely, killing this battery.

And it was accumulating about two and a half to three

amp draw on this thing and killing it, you know, over the course of a night or two.

So I went right from measuring total draw out of the battery to my network.

I'm skipping ahead there because normally when I describe my process,

which I even have in the class, is I'm using the amp clamp.

I'm figuring out which path out of the battery is the current going to.

Is it the, you know, under hood fuse box?

Is it the under dash fuse box?

Is it the alternator? Right.

I'll move the amp clamp around and I'll figure out the path.

And then I'll start testing at that component, you know,

12 volt to drop the fuses, maybe depending on what it is unplug it,

whatever I need to do in order to determine from that component.

It's usually a power distribution center.

Where is the current going from there?

But I'm not doing that in this case.

In this case, again, I went right to the network and I watched it

and I'm waiting and it takes a little bit of time to wait.

But again, that two and a half, three amps should be.

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

So I strongly recommend checking out L one training dot com.

The link is in the show notes.

Gone within 10 minutes.

It really shouldn't take it much longer than a couple minutes

for it to drop down below that point.

You're going to hang at that like 250 milliamps for quite some time.

But two, three amps should not be the draw on the battery for very long.

That is not normal.

And again, it's an accumulation of multiple modules

staying away, talking on the can bus.

And again, four different networks on this vehicle, they were all active.

So I'm actually surprised the draw wasn't more.

But I'm sure in an ignition off state,

certain modules aren't going to be drawing too much current,

but they're still talking on the bus.

There's still traffic everywhere.

But now this becomes a completely different diagnostic.

I need to, number one, figure out, well, which network is talking first?

And then number two, which module on said network

is the one that's talking now?

This one was acting in a way that I've seen

failures on Ford modules before where it would actually let

the current draw on the battery drop down to about 250

for maybe 30 seconds or so, and then it would pop back up to three amps.

And if you go way back in my case studies to one of my earliest episodes,

I have a Ford edge that I did this diagnostic on.

And it was same thing.

All the networks were awake.

It would go to sleep or try to it would hang in that 250

and then it would jump back up to three amps once everybody was talking.

And if you watch the network, you could see the same thing.

You would see it go quiet.

And then all of a sudden there'd be traffic there.

Same thing on this Lincoln.

This is a 2016 or 17 Lincoln MKX.

But, you know, similar network architecture as that Ford edge,

even though it's a little bit older.

But what you can do in a situation like that, where you have a network

that is waking up and it wakes up everything else,

because what's happening is whatever network is talking first,

that network is connected to the gateway module and other gateway modules,

like maybe an instrument cluster BCM and APM who are connected to multiple modules.

And somehow through the connection, I don't know exactly who does what.

I would imagine the gateways probably responsible for a large amount of this.

But that one one can network starts talking.

All of a sudden all of them start talking.

And if you're just looking at it on like a big time base on a scope,

you're just like, oh, they all started at the same time.

This is where a multi-channel Pico comes real, comes really in handy

is because you can set up four channels on four networks

and doesn't matter high or low.

I don't care.

Just pick a side of a network, get yourself set up and wait for it to turn on.

Like in this case, again, it would go to 250 and then it would pop back up.

Look at which one starts talking first, right?

If you're going left to right across the screen,

you're just looking at who moved first, which network had activity on it first.

And it was the high speed can two on this one.

We saw a blip on that one.

And then yeah, in like human time, it all occurred at the same time.

But on Pico time, where we can zoom in, we can see that clearly

every single time high speed can two talks first.

So I can safely assume the module that is talking, keeping everybody awake,

lives on high speed can two, and that's what I need to find.

I don't care about the rest of the networks.

I'm focused only on high speed can two.

So I've now eliminated it down to that series of modules.

And now what I'm going to do is break that network up into sections

using connectors to make the network smaller or divided up into pieces

so that I can say, OK, these four modules are on this side.

These four modules are on this side.

I'm going to break it apart.

And then I'm going to watch each side of the network

and see, OK, which side is still waking up or talking.

OK, now I've reduced it down to that many modules.

Now, one thing I will caution you on well, two things, actually,

if you're using a large connector to separate the network

because you've got the two can wires that go through it.

Number one, be conscious of what else is on that connector.

You may be killing power to something important and getting false test results.

That's a possibility. OK, here's the other thing.

And Ford likes to do this for Lincoln.

They will run that network through the same connector twice.

And you want to be aware of that because you're actually splitting

the network in two places.

That's fine. If you know, you can test appropriately,

but it's not always really clear on the diagrams

unless you're paying attention that they double back

and go through the network or through the connector at two different wires.

So you have like four wires of the same color on the same connector

and you've separated in two spots.

So just be aware of that if you're going to separate it this way.

There are times where I will choose to cut the network wires

if I don't have a good way to split it.

Now, I will also weigh that against how many modules

am I going to eliminate by doing this and how hard is it to access said modules?

If it's easy enough to just unplug the modules, sure, I'll do that.

But as all of us know, that's not the easiest thing of the world.

Sometimes getting to these modules is a ton of work in itself.

And I'd rather divide up the network this way and use the traffic on the network

because once the module who is talking is no longer on the network,

everybody else goes to sleep like, OK, we're done.

Let's go sleep until we get ignition wake up, right?

So we break it down further and further until there's only a couple modules

left. And this one ended up being the transmission range control module

that's up underneath the right front fender.

I've done some transmission range control modules on Ford,

never one in this exact location.

It was actually really tough to find.

Like, you can't see it until you pull that inner fender cover off.

And it was just the module that was waking up and going back to sleep.

You do want to look to see are there any inputs to a module that are

keeping it awake? I had a Ford escape recently where the button

for the steering wheel was intermittently pulling the circuit

down and waking up the cluster and keep in the cluster was the thing

keeping the network awake.

But it would have been very, very easy to call a cluster on that one.

But it was a switch on the steering wheel that was the problem.

So you do want to look at all the circuits and, you know,

what could potentially be keeping this network or this module awake?

One thing that you can do if you're not sure is take the module out of the vehicle,

just put power and ground to it wherever it would be getting it in the vehicle.

And it's going to have to have a constant power and ground

in the vehicle in order for this scenario to be happening.

So you can do the same thing on the bench.

And then you can monitor the comm lines right out of that module

and see if it wakes up all on its own, right,

with nothing else connected to any circuit.

Obviously, there's probably some nuances and caveats to that test,

but it's something that I'll use to prove to myself that, yeah,

that that module keeps waking up all on its own.

It needs no other input from the vehicle.

And if it doesn't do it outside of the car, but it does in the car,

you might really want to consider, hey, what am I missing here?

What other inputs could be coming to this module?

But here's the deal.

What I was talking about there from the start of looking at, you know,

seeing which networks talking first, splitting it up at connectors, all of that.

That's network diagnostic stuff, right?

That's the same if I had a module that was corrupting a network, right?

I had one module that was causing a problem on the network, disrupting traffic.

And I'm breaking down the network in order to find it, right?

It's short to power, short to ground on the network.

I'm going to break it down to sections until I find the one.

And I mean, even same thing.

Once you find that module that's corrupting the network,

I need to test powers and grounds to make sure it's not a, you know,

bad ground that's causing the corruption of the network because that can happen.

And that's all network stuff, right?

It completely switches at that point.

And that whole diagnostic after the initial look at the AMP clamp,

I did not care about the actual AMP clamp until I was done.

Until I unplugged that module and I went over, I watched it.

I'm like, OK, you know, network activity is no longer there.

And our amperage drops down to 50 milliamps where we want it.

Great, cool.

But again, I never even pulled out the amp out on it.

So where I'm going with that is for modern vehicles,

if you're looking at parasitic draws, just really, really consider,

I got to look at the network on this vehicle as I'm setting up for the test

and just be prepared to switch gears to you're really trying to break down.

OK, who's talking on this network when they're not supposed to?

And then why?

And it's a different path.

Now, the other thing I played around with a little bit

and some other people out there have as well is when you have a module

that is waking up on a can bus.

Well, I should say, when you have a module that's talking on a can bus,

it's going to use an identifier at the beginning of the message.

Now, there's a lot that goes into this.

I have a video on setting up the serial bus decoder in Pico.

If anybody's interested, I can share that, but it's pretty straightforward to use.

And modules can use different IDs or I should say modules can use multiple IDs.

They're not always going to have the same identifier for every single message.

But here's what I found when you have a module that is just waking up.

It's usually going to be the same message every single time that it wakes up.

OK, and it's going to have the same identifier.

And the identifier is relating to that particular module.

Now, what's in the data packet?

I don't know, what does the identifier mean beyond numbers?

I guess it just refers to that module.

Maybe it has some bearing on the message that it's sending.

It doesn't matter too much to me.

But here's what I do know is looking at modules

across a similar vehicle platform.

I've seen that the same ID is used for the same type of module.

And let me give you an example.

So that forward edge I was talking about way back when it was a tire pressure

control module that would wake up and then go back to sleep.

Very similar to this module I just diagnosed on this Lincoln,

but it would wake up and go to sleep.

And looking back at the waveforms that I had captured from back then,

the ID of that message every single time that module woke up was the same.

OK, now I looked at another forward edge

many, many years later in preparation to teach this class.

And it was a similar year to that one.

I think it was like a 2011 or something.

And I looked at the tire pressure module and you might say, well,

how do you know which one is which?

You can look at a dead can bus and you can force a module awake, right?

Give it power to the ignition feed and then or unplug it and plug it back in.

And it's going to be the first module that talks and you can see that ID.

The other thing you can do is watch the full can bus traffic with all of the modules.

You can filter the ID to the one that you're looking for,

pull the fuse for said module and see if it goes away.

It's another backwards way of figuring out, OK,

who has this identifier for the can bus message?

Take some time.

It's not exactly a quick thing, but you can do it.

I also looked at my Ford Transit Connect, which is 2012.

Actually, we have several of them.

And the tire pressure module has the same ID as the Ford edge of a similar year.

Now, does that mean every single this applies for every module and every Ford?

No, not at all.

I'm sure there's examples where it's not going to be true.

But here's what I've been doing when I find situations like this

where I have a module that continues to wake up and talk on the bus.

I will just capture that identifier and I will write it down in my notes for future use

so that if I run into another Ford edge with a TPMS unit that's talking,

I already know the ID and if it ever happens on a Transit Connect, I also know the ID.

If I see a telematics module on a Lincoln MKC waking up the high speed can bus three,

I have that identifier documented and I will be able to identify that

just by the first time that it wakes up and will go immediately to that module.

There'll be no breaking down of the network.

Same thing on this transmission range control module on this Lincoln.

I just diagnosed.

So these are all Fords.

So I guess I haven't had an opportunity to utilize this on another brand,

but Fords seem to be very common for issues such as this.

And so all I'm doing is documenting that ID.

Do I ever use it again?

Maybe not.

It's possible that is completely useful, useless information,

but I've already got my Pico out most likely for the DIAC.

And it takes me maybe 10 seconds to set up a serial decoder.

Look at the first message, write it down, put it in my notes.

It's not costing me a whole lot to document it.

Now, if you really want to go crazy and you work on the same platform all the time,

you could figure out the IDs for every module on a particular can bus

on a vehicle and document all of it.

I haven't found that to be necessary or for me to have the time to do that.

But it's something you could do.

So that's just a little extra there.

Again, I got that stuff in the class that I teach.

If anybody's ever interested, I'm sure I can figure out something to do that online.

But that's where I'm going to wrap this up, is that modern parasitic draws

are really just network diagnostics in disguise.

So I like to thank everybody for listening.

Hope you have a great Christmas holiday season.

We'll get one more episode out for the end of the year.

But that all the way.

Let's get out there, start fixing the world one car at a time.

Ford Edge

Lincoln Mkx

Ford Escape

Ford Transit

Lincoln Mkc

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