2016 Silverado Spewing Faults - Electrical Issue

[Timmer66]

A couple of weeks ago I drove my 2016 Silverado Crew for about 3 hours in a heavy rain with lots of road salt and temperatures hovering around freezing. At my destination I parked for about an hour and when I returned to start the vehicle it threw up a bunch errors on the dash; trailer brake issue, Stabilitrak issue, power steering issue, blah blah blah, but then it simmered down and drove fine for an hour to my next destination. Long story short, it repeated this over the next couple of stops getting progressively worse as the evening wore on and eventually the engine light came on and it went into limp along mode. At this point I had little choice but to make a run for it and head to my final destination about 60 km down the highway. Unfortunately it totally died about half way there, no dash lights, nothing. I had the vehicle towed to a dealer I had dealt with (late Saturday night) and waited to call them on Monday. Interestingly the truck started again when I tried it but I'd had enough excitement for the day so just left it.  Apparently the truck started on Monday morning and after spending 5 hr. looking into it and taking it for a 60 km test run they said though it had 18 pages of error codes they couldn't find anything specifically wrong with it and no longer being under warranty I think they didn't want to run up a huge bill with the risk of having nothing to show for it so they charged me for an hour and a half and sent me on my way. I suspect being in a warm  shop dried out whatever was causing the issue. Once home I researched all the codes on the work order and they all turned out to be communication faults on the CAN Bus network;  CCM can't communicate with ECM, EBCM can't communicate, TCM can't communicate etc. etc. Figuring this wasn't over I bought a code reader and did some research so I'd be prepared should it happen again and maybe reset the codes. For the next 500 km it ran fine until the day I set out for another 3 hr trip in rain and drizzle and a little over 2 hours into the trip it started barfing up faults again. The engine light came on however it didn't go into limp mode or die. When I got to a safe place I stopped and checked the codes. It was pretty much the same scenario so I cleared the faults and the engine light and carried on completing the final 70 km without incident. At home I parked in the driveway and when I came out 20 minutes later to dig in it wouldn't start at all and the code reader couldn't connect. My prime suspects at this point were the CAN bus and salt laced rain water.  My first step was to check pins 5 (signal ground), 6 CAN-Hi and 14 CAN- Lo on the OBDII connector. If all was well, there would be 60 ohms resistance across 6 & 14 and megaohm resistance from them to ground. What I found was no resistance between any of them indicating they were essentially shorted together with the ground.  I decided the easiest thing to get at was the chassis control module at the back above the spare tire. I pulled apart the connector and confirmed 120 ohms on pins 26 and 29 which is the back end of the network and no leaks to ground so that was good however the incoming pins 27 and 28 indicated the same states as the ODBII pins. Next I found the Electronic Brake Control module and noticed that whoever had worked on it left about 4 inches of exposed wires into the connector (sloppy) and there was wet road sand visible up inside the back of the connector and on the wires leading into the pins.  I took a spray bottle with clean RO water (barely conductive) flushed all the sand and salty water (very conductive) out of the back of the connector. Once it was clean I pulled the connector off, and inside it appeared to be dry though the tech had slathered dielectric grease over the face of it making it difficult to be 100% sure. I then confirmed 120 ohms on the inbound pair of CAN Bus wires and 120 ohms on the outbound wires which when connected together gave the requisite 60 ohms overall.  Coincidence? Maybe.

I then put the connector back on the EBCM and was able to start the truck. At this point I believe this is my problem spot however because the problem is somewhat self correcting it's possible there is another issue and the timing was coincidental but my confidence is fairly high. I subsequently wrapped the wires and took steps to reduce the ability of water and dirt to get into the back of the connector. I also added a dab of dielectric grease to the CAN wires where they enter the connector from the back. So for now I will carry on and see what happens though I will be keeping my code reader and multi-meter handy when I'm on the road.

 

I've attached the CAN Bus schematic and a couple of before and after pictures of the connector wiring in case someone is interested. Something I noticed when putting it together was that the red retaining tab on the connector had been broken off necessitating the second larger tie wrap in the picture to ensure the connector doesn't come undone. I imagine someone pried the connector open not understanding that the red locking mechanism needed to be pushed back first. Hmm. I'll post an update if this reoccurs. If anyone has any insights I'd be happy to hear them.

 

 

 

 

 

 

 

 

 

 

[silveradosid]

will be waiting for an update, friend has a 2017 doing this

[stulin]

I had very similar problem with my 2018 gmc 1500 Crew,last november ,driving in rain /snowy conditions and road salt .pulled over for quick break and truck started throwing all kinds of codes... Stabilatrack, trailer brake ,Steering codes ...also ran rough and started  shifting very hard ...took it to dealer and they found a data link wire  that had broke in wire harness going to back of truck tucked up in frame ...fixed it and hasn't missed a beat since .cost me $280.00 ...truck is off warranty. 

[Timmer66]

17 hours ago, stulin said:

I had very similar problem with my 2018 gmc 1500 Crew,last november ,driving in rain /snowy conditions and road salt .pulled over for quick break and truck started throwing all kinds of codes... Stabilatrack, trailer brake ,Steering codes ...also ran rough and started  shifting very hard ...took it to dealer and they found a data link wire  that had broke in wire harness going to back of truck tucked up in frame ...fixed it and hasn't missed a beat since .cost me $280.00 ...truck is off warranty. 

If the connector isn't the issue then it's probably a wire issue as was your case. Unfortunately the dealer couldn't find a problem with it so the trick is going to be catching it in the act which likely means pulled off the road somewhere in a rain/snow storm. Yippee!!  If I can figure out where a couple of the other modules are and if they're accessible I can potentially discern whether the issue is fore or aft of that point and hopefully narrow the search. In the meantime I'm not loving driving a vehicle that could die at any moment.

[Timmer66]

The saga continues. Drove 300 km without issue. First half was light snow and second half was mostly dry road. Started to snow about the time I parked and when I returned to the truck 3 hours later, it wouldn't start. Left it for another hour and it started. Pulled a huge list of codes but basically communication faults galore. Cleared codes and drove 10 km to overnight accommodation. Headed out in the morning in heavy snow for 300 km return trip. About 15 km out it started faulting and went into limp along mode. Cleared faults and continued. Repeated this a couple more times before it finally died for good. Had it towed to my house about 80 km away. Still wouldn't start then, nor in the morning. After sitting in the warm sun for half a day it started again in the afternoon. I haven't cleared the faults. Its getting towed to the dealer in the morning. Along the way I pulled code reports and looking at them the recurring theme is ABS control module communication faults. Also when it was home and wouldn't start I pulled the connector off the ABS controller and the vehicle would start. Put it back on and it wouldn't. I think I've found the smoking gun but I'll have to wait for the dealer to look at it. It looks like the ABS is bringing down the network. 

[Timmer66]

Headed out tomorrow on slushy roads to test the fix but looks like it was a nick in the network data wire just in front of the rear wheel. The wrapping had loosened up allowing muck and salt water into the cable bundle where the issue was. I think is was damaged in manufacturing as there were no other signs of abrasion on the other wires. Fingers crossed but I think this was the culprit. 

[silveradosid]

thanks for the update

[BlaineBug]

South Main Auto on Youtube has mentioned seeing a lot of issues with wires breaking inside of perfectly sound harnesses on newer GM vehicles.  Heard him mention it in one of his videos last week.

[Timmer66]

Certainly a plausible explanation for the issue you’re having. 

[BlaineBug]

Have you been able to trace the wire that you found damaged to find out what it controls?

[Timmer66]

Drove 200 km today on sloppy slushy roads without an issue so optimistic I've got it fixed. Yay!!

As for tracing the wire I do know precisely what it is. The white wire and the blue wire beside it are twisted together and make up the primary data network that runs between all of the major control modules of the vehicle, starting at the Engine Control Module and ending at the Chassis Control Module. You can see the wires in the diagram at the beginning of this post. They are identified as 2500 and 2501. As you can see they also pass by the Transmission Module, the Body Module, the HMI module and the ABS module. Any issue with either of these wires and the communication between all those modules is affected. In my case the wire was leaking to ground so all communications were toast. If the wire simply broke, you would probably get communication between the devices on each side of the break but not across the break.

Edited February 29, 2020 by Timmer66

[BlaineBug]

Well that's a dang swell wire to find damaged!  Please let us know how things progress over time, although I highly doubt you'll ghost us and disappear like some one time posters.

[Zack ferris]

I have a 2016  Silverado with the same issues but sometimes it would do it when the weather was dry. I found some very helpful information on this forum and thought I would share what I found where the wires go around the front box mount I found it. It rubbed through one of the wires. And where the rear tab mount is on the driver side I found three chafe wires, including a communication wire. It’s a blue and white twisted pair of wires one of the blue wires out of the pair was corroded and was sometimes making a connection and sometimes not I fixed the wires and so far so good I hope this helps