4wd not working 2002 Tahoe

[Sarahwv]

Im not sure what else to do with this vehicle. We bought it from an old friend who never used 4WD. We've put a new switch (the part inside that push button switches from Auto, 4wd and 2wd), 4WD transfer case module and 4wd actuator motor. It will sometimes switch into 4wd but will not switch out, then the lights turn off on the switch and the "service 4wd" starts flashing on the dash. When it does switch, you can hear it switch and it drives normal. The last fix was the TCCM, thinking thats why it wouldnt switch in and out. Changed it out, it shifted perfect, but halfway up the driveway it flashed "service 4wd" and locked itself in. Had to disconnect the battery to get it back into 2wd.

Any other ideas? We are in a pretty rural area and need this vehicle to have 4wd, especially in the winter.

 

[Fless]

The "service 4wd" message on the dash indicates that a chassis code was generated (like C0327, for example). You'll need more than a regular OBD code scanner to see which code it is, one that reads chassis codes. Once you get that code, post it in this thread so we can see what it pertains to.

 

[Scottydoggs]

id start with a scan. your normal code readers not gonna find this issue tho.

 

[strutaeng]

Im not sure what else to do with this vehicle. We bought it from an old friend who never used 4WD. We've put a new switch (the part inside that push button switches from Auto, 4wd and 2wd), 4WD transfer case module and 4wd actuator motor. It will sometimes switch into 4wd but will not switch out, then the lights turn off on the switch and the "service 4wd" starts flashing on the dash. When it does switch, you can hear it switch and it drives normal. The last fix was the TCCM, thinking thats why it wouldnt switch in and out. Changed it out, it shifted perfect, but halfway up the driveway it flashed "service 4wd" and locked itself in. Had to disconnect the battery to get it back into 2wd.

Any other ideas? We are in a pretty rural area and need this vehicle to have 4wd, especially in the winter.

Hey, welcome to the forum!

I replied to your other same post on pt.net before I came across this one ...

 

[Sarahwv]

Hey, welcome to the forum!

I replied to your other same post on pt.net before I came across this one ...

Saw that, thanks!! Gonna look into the encoder motor but will also look as finding someone to check the codes. Our code reader doesnt run those codes but we have a friend that may be able to. Just gotta get him out here.

 

[rockola1971]

Saw that, thanks!! Gonna look into the encoder motor but will also look as finding someone to check the codes. Our code reader doesnt run those codes but we have a friend that may be able to. Just gotta get him out here.

TCCM is likely lost because of a dirty or faulty Tcase Position Sensor (commutator) that is built into the shift moder (but is replaceable). This is the most common fault with the symptom you have. Doesnt hurt to get the codes that are thrown before throwing parts at it though.

 

[InterceptorF]

You might try to pull the TREC fuse and unhook the battery for like a whole overnight. That should be enough to drain down the TCCM or whatever circuitry it is that needs to reset. Then stick in the TREC fuse (30 AMP) and hook up the battery and see if it starts acting normal but like these guys are saying without that code its just a guess at what's really wrong.

 

[Sarahwv]

Just a quick update on this. We replaced the Transfer case shift motor and that seems to have done it. We're about a week into the fix and its running with no issues.

Thanks for the advice, looks like we're fixed!