So as the title states I am dealing with a four wheel drive issue. No lights on the dash and I can not communicate with the transfer case control module. Scanner says it is a class 2 communication failure. I have power and ground to the TCCM I also checked all fuses and they are all good. The truck just goes into four wheel lock on its own randomly. No rhyme or reason for it. Any help would be greatly apricated.

Ryan

 

You have an electrical issue. Yeah you figured that out. Post the actual code(s), not your synopsis.

Until then, track it down. Check the T Case switches, people spill coffee, juice, who knows what on them and they get stuck in position or shorted, etc....

Get under and look at the T Case Actuator Harness for frays, faults, cracks, and wearing. Check its connectors, clean with CRC Electronics Cleaner and reconnect. Same thing up at the dash switch end.

Do you have a sunroof? If so, has your passenger floor ever been wet? If, so do the fix to the clogged sunroof drains and then inspect the TCCM connectors and harness for corrosion.

 

Checked T case actuator connector and all was clean and corrosion free. T case swtich lights up and does what I believe it is supposed to do. The TCCM in the dash is also corrosion free. This hummer has a sunroof but it does not leak. Floor is bone dry.

 

You stated before no lights on the dash? Do you now have a light for the T Case Buttons, the Pssgr Air Bags status?

Might want to do some reading on the Plastic T Case Fork issue. Could be you.

 

My apologies. I meant no service 4 wheel drive lights. Yes the 4x4 panel seems to work as it should. I did order a new one just to rule that out. I still can not communicate with the TCCM. The fork issue I am up on. I pulled the front drive shaft and sure as **** it drives in all modes. I know that it is not supposed to.

 

OK, I get it now. Pretty sure you have the fork issue. Since it is not working to move the lock/unlock collar, or possibly does not have it in the correct anticipated position, your TCCM cannot detect what is going on = nothing to report/no communication. Unless you find a break in the electrical harness, I am leaning T Case Fork need to be updated to the newer metal replacement.

 

I greatly apricate your help. I truly enjoy this old alpha. It goes great besides this issue and I found the front diff bushing is on its way out. That is a easy fix

 

From what I've seen around the 'net, it is not fun, assuming we are talking about the same thing. Post some pics and notes when you do this job.

 

Clean or replace. Look here--->>>Transfer case switch