Another 2002 TB 4WD ?

[se1911]

I've recently replaced the 4WD disconnect after it decided to shatter. Everything worked good after that. My son normally drives this, so fast forward a few weeks. I get in and notice the selector switch is on AWD but the light is on 2WD. I change the switch to listen for the 2 different sounds when changing modes. No sounds at all. The light blinks for the new position of the switch, then goes out. The light remains on 2WD. The service 4WD light is not on. All lights on switch come on then go out when starting. I couldn't find this specific situation any other threads, sorry if I missed it. I'm thinking TCCM, but would like other opinions. Thanks for the input. It has about 150K on it. Fluids replaced at 100K, so time to do it again.

ETA: I pulled the #8 fuze and nothing changed.

 

[The_Roadie]

Welcome! Glad you found us (did you go to that "other place" first?)

The transfer case encoder motor could have broken a planetary gear inside and frozen up. Less likely is that the transfer case is gummed because its change interval is every 50K, not 100K.

But your total lack of motor sounds, even in the 2WD->A4WD transition, which is the one that moves the front axle actuator, sort of implicates the 2002 TCCM. They were notorious for losing communication with the PCM, which is what usually lights the dash lamp and causes the switch lights to go out. But they can also fail in a way that leaves the dash lamp dark. See if you can find a buddy to change with for an experiment.

How long could he have been running around in the damaging A4WD mode without knowing it? That damages transfer case clutches, but usually doesn't cause your exact symptoms.

Also, put the switch in 2WD mode, pull the fuse for 30 seconds, then put it back in and turn the ignition on (engine can stay off). Then turn the mode switch to A4WD mode - do you get the actuator noise (high pitched whine) at all in that transition?

 

[se1911]

Welcome! Glad you found us (did you go to that "other place" first?)

The transfer case encoder motor could have broken a planetary gear inside and frozen up. Less likely is that the transfer case is gummed because its change interval is every 50K, not 100K.

But your total lack of motor sounds, even in the 2WD->A4WD transition, which is the one that moves the front axle actuator, sort of implicates the 2002 TCCM. They were notorious for losing communication with the PCM, which is what usually lights the dash lamp and causes the switch lights to go out. But they can also fail in a way that leaves the dash lamp dark. See if you can find a buddy to change with for an experiment.

How long could he have been running around in the damaging A4WD mode without knowing it? That damages transfer case clutches, but usually doesn't cause your exact symptoms.

Also, put the switch in 2WD mode, pull the fuse for 30 seconds, then put it back in and turn the ignition on (engine can stay off). Then turn the mode switch to A4WD mode - do you get the actuator noise (high pitched whine) at all in that transition?

Didn't look at the other place first. Last time I posted there I was told to come here.

Not sure how long it was in was in "damaging" AWD mode. Can you explain why it is damaging? If rear tires aren't slipping, is anything engaged?

Tried the #8 fuze, and nothing changed.

There are no local yards with any TBs or equivalent, so I'm looking on Ebay for a TCCM. Since they are listed as 02-05, how do I identify and avoid the hated 2002 version? Are the model numbers different?

Thanks for the input.

My son decided to back into an 03 blazer that we have. Now we get to replace the door and maybe fender on the blazer. That sure pissed me off. Taillight and bumper damage on TB.

 

[The_Roadie]

New good TCCM 12590220
Old bad TCCM 15085386

A4WD mode is bad in dry conditions because it partially engages the transfer case clutches to pre-bias some small amount of torque to the front wheels even when none is needed. That can and will cause premature transfer case failure. It is (IMHO) bad in snow and ice because when wheel slippage is detected, the encoder motor engages the clutches with a relatively fast onset rate that has been known to break a front or back end loose and CAUSE accidents. If it's slippery enough to need 4 wheels worth of traction, the driver should just commit to 4HI and get it over with. A4WD in rain is just wussy scaredy-cattiness, and unnecessary unless one is driving right at the edge of their traction limit, which shows poor judgement.

 

[se1911]

Thanks for the info Roadie. Pulled my TCCM out, and it has the new p/n on it. Is it worth replacing just to see if it is the problem? Any other way to troubleshoot?

Need to retrain wife/kids on using 4WD. No more A4WD.

Thanks Again.

 

[The_Roadie]

I've posted the schematics a few times here and on trailvoy. If you have some electrical troubleshooting experience, and a bit of knowledge on how the system works from the manuals linked here on this site or from the factory service manual, you can run through the checks and see what's wrong. It may be damaged wiring or still a bad TCCM. Only you know what your experience and patience and budget level is. Be glad to help talk you through it, though. PM me.

 

[se1911]

After replacing TCCM and troubleshooting the wiring, I decided to order an encoder motor. Installed the motor and now everything works.

I had neither of the distinct sounds from the encoder motor or the actuator switch. This leads me to believe there is a logic circuit that prevents the actuator switch from functioning if the encoder motor is not functioning. Now that my encoder motor is working again, the actuator switch is also working. Any thoughts on this?

 

[H2Oboy]

Been reading several post and this one sounds like se1911 problem is similar to what i have going on now. going to dive into this a little more this weekend. really crossing my fingers its a bad selector switch inside, but sounds like it going to be a bit more pricey TCCM or encoder motor.