2002 Trailblazer 4wd stumper.

[Michigantb]

Hello all,
I'm having the all too common 4wd issue in my 02. The service 4wd light was on and other than the bulb check at key on, I had no selector lights. I replaced the tccm with one out of an 05. This turned off the service 4wd light, but still no lights on selector, not even a bulb check now. I replaced the selector with a new one , no change. I went to the junkyard and got a tccm out of an 04 just to try it, it created the original problem, service 4wd light and only bulb check on selector. I put the tccm back in that turned off the service 4wd light. I used my autoengenuity to scan and attempt to communicate with the original tccm to no avail. Codes C0550 C0327 C0306 C0321 were present at that time. I took the tb with this 05 tccm installed to the chevy dealer and they were not able to communicate with it using the tech2. Any ideas? I haven't looked into the transfer case or encoder because I figured if you can't talk to the tccm, there is probably an issue there that needs to be fixed before even looking at the t-case.

 

[The_Roadie]

No lamp test indicates a dead TCCM that won't even pass its own power-up diagnostic. The failure to communicate may be a broken comm wire that might be troubleshot using the splice pack that's mounted to the back of the under-dash close-out panel in the same location as the TCCM, but it might be a bad power or ground wire to the TCCM so it doesn't wake up to be able to communicate.

I'd download the manuals and schematics from the thread here on GMTNation, whip out your voltmeter, and check the TCCM connectors for proper power and ground and data comm.

 

[C-ya]

Welcome to the forum! Did you take the truck to LeValley? I haven't had them do any work on mine that I had to pay for, so I was curious what they charged for the Tech2 time.

 

[IllogicTC]

Any luck on this issue yet?