Need help

[crazykid1994]

Any ideas? Bringing it in to Arrigo on Tuesday. Already had a new pcm installed prior. Trucks under warranty. Stalls out and won’t restart for a little bit. Has done it a few times in a row. More pictures in next post

 

[crazykid1994]

The instrument cluster seems to read more codes than the bcm.

 

[leowes]

Battery cables tight? Cables tight in power distribution box?

 

[Hemi395]

That's a lot of no comm codes, looks like something is taking down the canbus network...

Did you recently replace any modules?

 

[crazykid1994]

Battery cables tight? Cables tight in power distribution box?

Everything is tight.

That's a lot of no comm codes, looks like something is taking down the canbus network...

Did you recently replace any modules?

I have not. Only things I’ve done to the truck are v6 fan and put a leveling kit on it. I Took it to the dealer and they replaced the pcm already. That was a few weeks ago. Planning on bringing it back in for them to continue diagnosing it.

 

[crazykid1994]

Doing some research. Based on the fault codes. I’m curious if I don’t have a failure in the wiring harness. The power steering, abs, and tcm all communicate through the engine harness. The drivetrain control communicates through the dash harness. I don’t lose power to anything as far as I know so there is a good chance that it’s not the tipm. But I get the backup camera out as well and that communicates through the bcm and only receives power from the reverse signal at the tipm.

 

[Hemi395]

Doing some research. Based on the fault codes. I’m curious if I don’t have a failure in the wiring harness. The power steering, abs, and tcm all communicate through the engine harness. The drivetrain control communicates through the dash harness. I don’t lose power to anything as far as I know so there is a good chance that it’s not the tipm. But I get the backup camera out as well and that communicates through the bcm and only receives power from the reverse signal at the tipm.

Thats what it sounds like to me too. They could've bent a pin when they put the new pcm in or simply broken a wire.

Any evidence of mice under the hood? They love to chew important and hard to diagnose/fix wires....

 

[crazykid1994]

Thats what it sounds like to me too. They could've bent a pin when they put the new pcm in or simply broken a wire.

Any evidence of mice under the hood? They love to chew important and hard to diagnose/fix wires....

Problem is they replaced the pcm because of this issue. It’s an intermittent recurring issue that has slowly gotten worse. No signs of any wiring damage that I can tell externally. Hopefully Wednesday when I drop the truck off they can figure something out. I’m doubtful that I’ve had 2 pcms go bad. Unless it’s a communications node under the dash that’s going into failure. I had a failure driving home one night and my dash said comm failure and would flash but I could still drive. Didn’t have an issue for a while then it would randomly say comm failure and blink. Then one day my truck shut off on the way home. It restarted fine so I drove home. The dash is lit up but does not display any info. Temps won’t read. Just gets ———— next to it. As soon as it comes back up displaying temps I can start the truck. The truck won’t even try to turn over and no relay click but turning the key on and off turns all the electronics on and off. Almost like tipm or pcm failure but it’s intermittent which makes this an odd scenario. I’ve tried moving wires around to see if I can simulate the issue but no matter what I do I can’t simulate the issue. It gave a permanent code for ecm/pcm failure which is the same I had prior to the pcm swap. Currently the truck is running with no issues and the code is not pending. It’s very odd that it will clear itself and the truck starts running again.

 

[Hemi395]

Yeah that sounds like a wiring or connector problem. Way too intermittent to be a 2nd bad PCM. It's also possible another module is going bad which is randomly killing the canbus network.

Modern vehicles are fun[emoji849]

 

[Hemi395]

Check all the grounds as well. Theres a bunch on the passengers fender and some more on the frame rails...

 

[Tim Garceau]

Grab your multimeter and perform continuity tests tracing the code path(wiggle wires/connectors if intermittent) based on the wiring schematics. This is one I definitely wouldn’t leave in the hands of the dealer unless you knew they had an electronically savvy tech.

Otherwise it’s going to cost an arm and leg with them guessing and checking new components.

 

[crazykid1994]

Grab your multimeter and perform continuity tests tracing the code path(wiggle wires/connectors if intermittent) based on the wiring schematics. This is one I definitely wouldn’t leave in the hands of the dealer unless you knew they had an electronically savvy tech.

Otherwise it’s going to cost an arm and leg with them guessing and checking new components.

I’m going to give them the chance to fix this since it’s under warranty. If they can’t fix it I’ll dig into it more. Hopefully they can get it figured out. Not much comes up in the codes which sucks but what does come up almost feels like a canbus module. There is a bus module under the steering wheel and one under the passenger side that are part of the main bus. I’m trying to do some research on the communication to see if there is a way to test these modules. There should be a certain voltage across the wires if everything is proper. Being that my issue is intermittent I’m sure that everything will read fine. I have a feeling it’s a module failing but which one. I’m giving as much faith as possible to my dealer. They seem to be very pleasant to deal with so far.

 

[Tim Garceau]

There are some good ones out there, keep us posted.

just saw you’re an electrician, Can the canbus Modules be tested independently with a power supply?

 

[crazykid1994]

Sorry for the picture quality.... had to take a picture of my tablet since my phone won’t open pdf files. This is a schematic of the canbus system. I need to find the star can c dash module that links all the items together. It appears according to this that that module communicates with the abs, power steering, drivetrain control, and the transmission control. All of those appear in my scanned codes.

 

[Hemi395]

Any idea where in the dash that is?

 

[NETim]

Make sure your 120 ohm terminators are installed on either end of the bus.

 

[crazykid1994]

Any idea where in the dash that is?

According to the layout I have, it’s under the passenger side dash close to the Firewall near the pcm. To wet outside for me to try and do any looking.

Make sure your 120 ohm terminators are installed on either end of the bus.

any idea where or how to check for this? I’m looking into the information I have to find out what voltage and ohm readings I should have across the module.

 

[NETim]

According to the layout I have, it’s under the passenger side dash close to the Firewall near the pcm. To wet outside for me to try and do any looking.

any idea where or how to check for this? I’m looking into the information I have to find out what voltage and ohm readings I should have across the module.

I don't know where they are physically, but I found this troubleshooting guide for CANBUS systems, that might help.

https://www.orionbms.com/general/diagnosing-canbus-communication-problems/

https://www.esd-electronics-usa.com/Shared/Library/CAN-Troubleshooting-Guide.pdf


CANBUS networks are by no means unique to automobiles, there are some helpful guides out there on the 'net. I got spoiled on my medical imaging systems as they were usually loaded with all kinds of status indicator LED's and usually some nice diags loaded on the system. I got spoiled.

 

[crazykid1994]

This is the can c star Module. It’s under the passenger side tucked up next to the fan blower. If it stops raining then I can try and ohm the wires to check for continuity.

 

[Hemi395]

This is the can c star Module. It’s under the passenger side tucked up next to the fan blower. If it stops raining then I can try and ohm the wires to check for continuity.

View attachment 208970

That's funny, it literally looks like a mini Ethernet switch[emoji23]