Originally Posted by christine_208

Sorry to interject and slightly high-jack this thread but perhaps the answer to my question could be considered relevant to this discussion and would be one from which others would benefit.

Lesmeyer, I replaced my TCCM last year with a NOS GM TCCM with a part number appropriate for my year, model and type of system (4-button). Should I have done something to program it? It seems to be operating just fine for me.

Originally Posted by Lesmyer

4WD switches don't typically give many problems. Here's some specific info for the 2001 4-button system.

Did you check the ATC fuse in the under the hold relay center? There are multiple fuses for the 4WD system. ATC is the main fuse that powers the TCCM and the encoder motor. Without it, you get nothing.

TCCM supplies an 8V reference signal to the switch. Depending on which button you push a different voltage is returned back to the TCCM and it will attempt to move the encoder motor and transfer case to the appropriate position. This is the primary 4WD control circuit. Front axle locking in is separate.

The brown wire you speak of only powers the lights in the buttons of the switch - and they will never light up or flash until the TCCM is happy decides to provide a ground for the individual circuits for the lights. TCCM no worky - then no lights in buttons.

https://blazerforum.com/forum/2nd-ge...-blazer-89044/

A common problem is the power connection (big red wire) at the TCCM gets corroded and does not make a good connection. Sometimes cleaning this can cure 4WD issues - certainly it is one of the first things to check. Often the encoder motor burns up and blows the ATC fuse. Keep in mind that since the power for the encoder motor passes through the TCCM, it can be damaged as well. Switches are typically pretty trouble free.

If you end up needing a replacement TCCM, know that they are programmed with info specific to your vehicle. GM ones do not come pre-programmed. Cardone units do. Note this statement is apparently wrong. See next post.

good luck and best wishes for a successful repair.

Originally Posted by Graveyard

If you end up buying a switch, go to walmart.com and do a search for your model. I ordered one for my 96' blazer last nite for 16.34 with no tax and free shipping.
Anywhere else it will be double or triple the price.