Jim98TA

I'm trying to troubleshoot an issue on my 2004 Chevy Silverado ECSB with the 5.3 liter in it. It started on Tuesday morning out of nowhere. The truck was fine on Sunday night/Monday morning.

The issue affects numerous things, the following all go out at the same time:

• Gas gauge, voltage gauge, temp gauge, oil gauge
• radio shuts off (sometimes stays on)
• ABS, Brake, Security, Voltage lights come on
• Power windows/locks quit working
• steering wheel controls don't work
• 'unknown driver' message come up
• trip computer info gets weird
• scanner unable to communicate with data port

Pulled the codes on the vehicle and got BCM info, etc. saw a ton of things in there and we cleared them out. When it flipped out again we checked the codes again. We got the following:

• U1000 - Class 2 Data link malfunction
• U1305 - Class 2 Data link low or high

Things I've checked so far:

• Grounds under driver door, sanded clean, reinstalled
• Unbolted and bolted back on the ground behind driver tow hook
• Alternator tested OK at Autozone
• Battery passed a load test
• Pulled dash apart and verified connections on modules
• removed seats to verify wiring under seats not worn through
• checked fuses

Other info about vehicle:

• Remote starter has been installed for 1.5 years (I disconnected connection to data port purple wire and it made no difference)
• factory 6-disc head unit installed about 2 years ago
• stereo system connected to factory head unit (been installed for about 9 months (verified grounds on system and seem OK)
• electric fans have been installed for about 3 years

Anyway, if you are still reading this, I am about out of ideas on this one. If anyone has any similar experiences, or ideas what might cause this, I would greatly appreciate the help..

Also, if anybody knows a way to troubleshoot the class 2 communications info, that could be of great help.

01WS6/tamu

iTrader: (36)

You need to have a tech 2 and see if you can communicate with each and every module in the truck. It sounds like a comb connector may be giving trouble. Thats where all of the databus wiring for all of the modules come together. If you cant talk with a module then that is the circuit that will be suspect.

Jim98TA

I took it over a friends house last night and he has a Snap On scanner. We were able to communicate with the Engine, Transmission, ABS, and BCM modules. However, when the issue comes up, nothing can communicate with the truck. Its like the data port goes dead.

Are there other modules besides those 4??

01WS6/tamu

iTrader: (36)

Driver door module, passenger door module, Instrument panel cluster, Airbag module, Body control module, powertrain control module, Radio, Bose amp, HVAC controller, onstar module, generator battery control module.

Jim98TA

Thanks for the info.

Oddly enough after the thing completely flaked out last week, it cleared up. I cleaned up grounds again, moved some wires/harnesses around, etc. So far it hasn't acted up again. If it starts again, I'll dig into things and see what I can figure out.

Robotech

I know this thread is ancient but I have this EXACT same issue on my 2004 GMC Sierra and I can't find out what is wrong with it.

Like the original poster has mentioned, I have cleaned grounds, taken apart the dash, wiggled things, nothing is working. I have no remote start or aftermarket radio. His symptoms though are exactly what I'm experiencing.

I know his solution was to wiggle some things and poof it worked but I was hoping...maybe...someone else on here may have had an experience with this and found where the problem was. I tired to connect to the OBD2 with a Craftsman reader but I may try my HPTuners and see if it will connect.

I'm just at a loss here. I haven't checked wiring under the seat but I don't know if this is related since I don't have memory seats.

Anything would be greatly appreciated. Thanks guys...

madmann26

iTrader: (7)

Check the fuses for the cigarette lighters.

That one prevented me from getting my emissions test one year. They couldn't read the computer in the truck.

Robotech

I'll check it but I had that happen to me too last year and I didn't have all these issues.

A4edwin

I've had the same problem with my Tahoe but for some reason it's only happened to me in hot weather. Didn't happen to me at all during the winter. I disconnect the battery and reconnect problem goes away for awhile the comes right back. I would really like a permanent solution.

About20ninj45

When i had that issue, it was from the hi/lo data lines having a short/break in the wire