Hello, last wekk I bought my son a 1999 Blazer/Trailblazer. After one week, he decided to take it offroad (which we had said he could not do yet). He got stuck, not bad...but stuck. Someone tried to help pull him out (from oppsotide side of a creek, he was stuck at edge of creek), to put it simply the moron wenched him right into the creek, which is about a 10ft drop. Now the right half of his truck was in the water, across the hood back to the front of the back passenger door (4DR). Once the wrecker got him out (other guy left after putting it into tcreek, saying he could not help), the truck would not go into 4WD anymore. Eventually as he was having to back out in 2WD through the original mud hole he got stuck several times, ripping tail pipe off, which cut the right rear brake hose in two and some other things...body wise. We fixed everything, but the "service 4WD" light is on andWD will not engage. I have been on thi ssite for days and have done everything mentioned on here, using the "search":

1. Took TCCM out and it was corroded, I cleaned it up top bottom on circuit board and the male/female connections. The circuitboard looks ok to me.

Results: When I put it back in the lights worked on the switch (which did not before, even when we first got it), but it still would not engage. The "service 4WD" light was not on, after driving a little bit trying to get it to engage, the light came back on....next was step 2.

2. I traced the vacuum hoses and found them to be old and some broken and the 5/32" hose that goes to the canister nipple was not connected to the nipple. So I replaced all hoses in that area (I will finish the rest tomorrow).

Before I move on to do the rest of the steps for testing the actuator and such, I want to ask. Do you think that the TCCM being in water could have made it go bad? Or am I getting closer as I contnue to fix more things? I am puzzled that the switch lights came on for a little bit, but now they will not.

Thanks,

 

The TCServo Motor is sealed, so getting it wet shouldn't be the problem.
What I've had happen with mine is that after I tried switching from 4wd to 2wd, I'd hear clicking from the TCCM, then I'd hear the TCServo motor spin for 3 seconds, then the Service 4wd came on and the dash lights went out. Mine ended up being a broken gear drive on the servo motor.
Do you hear relays clicking when you try selecting 2wd, 4Auto, 4Hi and 4Lo? IF yes, the TCCM should be working, and your problem may be the Transfer case Servo motor. I noticed with mine whenever I disconnected and reconnected the battery, the servo motor would spin for 3 seconds.
That shouldn't happen. Disconnecting the battery should reset the service 4wd, and should allow you to test for the above symptoms.

With the Service 4WD light on, you could always get the code(s) read at a service center capable of reading those(My pocket scan unit only reads engine dianostics-bummer). It will at least point you in the right direction as to what's causing the problem.