Im new here and looking for some professional help. I bought this truck new and it has been great until recently. Its a 2003 GMC 6.0 CCSB 4x4 2500HD... My truck has a electrical issue I can not figure out. I have cleaned all the grounds in the engine bay and the grounds at the frame under drivers door, checked all fuses.
When I first start the truck everything seems fine and driving is fine. Then within a few seconds gauges drop dead, come back, drop dead again etc. When there dead the power windows will not operate...radio stops working and security light starts flashing... almost all the warning lights on cluster come on. DIC displays, Service 4WD, Unknown Driver 1, right rear door ajar, left front door jar. Then as quickly as the problem starts it goes away. Then in a few seconds does it all over again.
It drives fine, headlights and turn signals work Took it to a friend that has a Tech 2 and it cant even communicate with the truck... my cheaper scan tool can not communicate with the truck either. If I cant scan it for codes..then what? Im at a loss as to what to do next with it.
Im guessing BCM is going out but I dont want to throw money I dont have at things that arent bad. Im extremely frustrated with this truck right now! ANY help would be much appreciated. Thanks!

 

BTW...its stock, no mods. Never has had any either.

 

I am not a GM tech but have heard similar stories. It is more than likely the BCM.

Jeff

 

I had one that had similar issues but it wouldn't start also. Ended up being a seat harness under the drivers seat shorting out the bus line. Pulled down all of the modules online. Unplugged it and everything worked. Just a thought.

 

Thanks Jeff... I was leaning this way as well, but with not being able to communicate with the truck via Tech 2 really bothers me. Maybe some one knows a way to confirm a bad BCM?

Thanks for the post.. I will be checking on this to see if it is a problem.

 

*Little Update* I unhooked the batteries completely this morning and left them unhooked for a couple of hours. Hooked everything back up and started the truck....all was looking good. My Actron scanner was communicating with the truck just fine with no codes, then all the sudden the scanner lost communication, and probably 30 seconds later all the same electrical issues again same as first post. Does this help diagnosis at all? Thanks again

 

CANBUS error most likely. In the event that you can't read codes, I would suspect an internal issue with the BCM or something is very wrong with the wiring. I'd get the documentation on the ring network devices and start unplugging them one by one to see if the problem stops. The PCM should still communicate even if the interior CAN is dead, though.

Alternatively, (and this is a bit of a long shot) pop your underhood fuse panel service cover (not the lid, the whole shebang) and see if there's a rat nest or damaged wiring under the main fuse/relay panel.

 

I had a similar issue, all gauges and radio stop working. It was a ground wire from engine harness to the back of the engine on the right side (passenger side) was broke loose.

 

My wifes 2003 Yukon with a 6.0L is acting crazy too. Radio stopped working yesterday but everything else was good to go. This morning I go out and it won't start, jump the truck and let it charge and the radio starts working again, the front ac isn't getting cold but the back is, the oil pressure guage won't go back to zero with the motor off and while on it reads way past 80psi and sometimes it will peg the guage.
I do know that before we got the truck a wire had come out of the harness under the driver seat, got the seat working but all this other crap keeps happening.