4x4 Issue

[Mike Comello]

I am having a 4x4 problem. I have done quite a bit of testing and here is what I am up against.

 

Press 4H on dash

Transfer case motor engages

4H light flashes (front axle/diff does not engage)

 

Turn truck off/on

 

Front axle/diff engages - 4x4 engaged (confirmed by having truck up on blocks and verifying wheels don't spin independent any more, also by reversing/turning on dry pavement)

 

4H still flashing

 

I have tried replacing the TCCM but was not the issue.

 

Now suspect that whatever indicates to the system that the transfer case motor has reached position is not sending signal back to TCCM to have it move/actuate front axle. And that somehow turning truck off/on by default has the front actuate.

 

Anyone with information on how the transfer case senses position? Or any details on this issue?

 

Thank you in advance, Mike

[00Silverado4x4]

If it's anything like mine, the sensor is a part of the encoder motor. Mine is mounted on the outside but yours could be internal to the motor. Not to insult, but have you checked all the fuses?

[Mike Comello]

Yes we checked fuses. There is not a separate fuse for the sensor and the motor. Motor is working/moving the transfer case. Just no feedback from what we can diagnose. Probably going to swap out the motor next.

[kstruckcountry]

Most likely the sensor on the motor.

 

But it would be better to scan the TCCM, and diagnose rather than wasting $100's on parts you don't need.

[Mike Comello]

Thanks guys. We did scan it. Although my friends scan tool does not show the feedback/position indicator of the transfer case or axle actuator . However there were no error codes in the TCCM and we could command each of them to move into the position we requested. Likely will replace the transfer case motor next.

 

EDIT - Found out there are 2 position switches on the transfer case and service tech said these are frequent causes

 

http://www.wholesalegmpartsonline.com/products/SWITCH-Transfer-Case-Shift-Control/3207156/97358605.html

[Alan Farrer]

Re:front axel not engaging

 

After the dealer telling me I'm the only one with the problems, and spending many thousand dollars, I took front left axil apart and found the shaft attached to the shift fork broken in half. New shift fork,- end of problems.

Alan