Ok, took it down to the dealer and it's a C0387 code, I believe same as before. The tech wasn't getting any codes at first even though the light was on and the system wasn't working so we swapped between the old and JY TCCM and finally he got it to come up. The truck will try to make the shift to 4 hi, but flash and go back to 2hi, goes to auto with no problems, but it's actually not working, the rear spins easy. When I try 4lo, you can hear the TCCM clicking, then no shift and lights out in switch and S4wd on in dash. I'm stumped and so was the tech.

Either I got a cheap korean defective part (dorman) or something else is causing it to go bad, or bound up and frying it. Wouldn't it pop a fuse first before burning out the TCEM?

 

C0387 - Unable to complete shift


You are going to have to get in and test things. It could be bad connections between the TCCM & Encoder Motor which could be impacting the ground(s)/power/returns to/from the encoder. The only way to really know for sure is to check the wiring and back probe the connections to make sure that everything is getting the appropriate power and that there are no drop outs in power or ground.

 

As you've read my thread:

https://blazerforum.com/forum/2nd-generation-s-series-1995-2005-tech-41/4x4-no-lights-switch-52923/

We have very similar issues although yours seems a bit more responsive. I goofed around with mine a bit yesterday and found that when I moved the wires down at the TCCM the relay(s) in the module would click, the S4WD light would also come on. Think I'm going to concentrate on how to get the electrical connections to the TCCM consistent, I'll probably redo both harnesses and put it in the glove box or behind it or something which I've heard of another person doing.

I found this site

http://www.kylestubbins.com/forum/19

previously which outlines a lot of other people having similar issues, only one I believe with the same as ours though, no resolution of course. Some nice schematics on it though which I found matched up with my 99 LT 236 TCase.

Will keep you up to date if I get mine fixed or where I end up in the snow bank if I don't

 

Have you checked T-case lube lately ?

 

Took mine to the dealer and they found the encoder motor was bad, code C0308. Replacing the encoder motor soon. Found an interesting link here for the code:

http://ww2.justanswer.com/uploads/Bl...rban_c0308.pdf

 

to update the thread. i learnt that a weak battery can be a problem causing this issue.

after getting a new dash switch, new module and new battery everything is fine now.