NEED HELP 4WD not working

HoldenEst

Original poster
Member
Sep 9, 2022
2
Estonia
Hi, I just bougt the '02 Trailblazer. Now I noticed that the 4wd is not working, although there is no warning lights on dash. I have read all the 4wd issue topics here, but don't seem to find solutions for my problem.

When I start the car up, ALL the lights on the transfer case swich light up for few seconds.
I turn the swich to AWD- no lights- no sound and lights up the 2Hi indicator on swich
4Hi - light blinks and light stays on, I can hear the transfer case motor and actuator working, but still only rear wheel drive ( I noticed it because got stuck in the sand the other day).
4Lo - same as 4Hi.

Now I tested the system that way: on the 2Hi I can turn the front driveshaft by hand, when on 4Hi or 4 Lo mode front shaft would not turn. I assume, that the transfer case is ok then?
The TCCM block on my car is 15085386, but as I understand, when the lights on the swich work it's not the module problem? (Except the AWD)

Yesterday I took the dashboard swich apart to clean it, I was nice and clean inside. I have turned the knob few dozen times, but no AWD light! I have pulled the #8 and #45 fuses - no luck.

I appriciate if anybody can get me some directions to diagnose the problems. In Estonia (It's where i live) there's few TB-s in salvage yard, but all of them are 02 models. So by getting the parts I have to order form e-bay or Rockauto.com
 

NJTB

Member
Aug 27, 2012
612
Flemington, NJ
If you have a Tech 2, hook it up. The Tech 2 can tell the 4wd switch position and is able to enable the encoder motor and axle disconnect motor, etc. Then go from there.
 

Mooseman

Moderator
Dec 4, 2011
25,262
Ottawa, ON
Put the switch to 4HI, jack up the right front wheel only and see if you can turn the wheel. If it turns, either your disconnect is defective, the intermediate shaft is stripped or both.
 

HoldenEst

Original poster
Member
Sep 9, 2022
2
Estonia
Thanks! It seems to be the disconnect problem. I jacked it up and when I spin the front wheels in 4Hi mode, the front drive shaft is not spinning, also I can hear some cliking noise from the area where the disconnect is.
But can that be related with the thing why my AWD indicator on swich is not lighting up. Or could it be that there’s more than one problem with the system?
 

Mooseman

Moderator
Dec 4, 2011
25,262
Ottawa, ON
The disconnect doesn't have feedback to tell the TCCM it's not working beyond just being disconnected. If the motor is working, it won't know. It could be a mechanical failure.
 

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