Hello again all,
Thank you for your help before.
I have a new problem I hope you can help...
My 2000 Trailblazer "Service 4wd" light came on when I tried to switch to 4high. Now.. NO indicater lights show at all on any buttons (2high/4high/4low/autoawd) Seems to be in 2high though...OK to drive...
Is it a fuse? Or something worse?
Thanks again

 

Tried pulling TCCM...cleaning conections...replaced...still, no lights on 4button display? Service 4wd light still on. Seem stuck in 2whdr. Read somewhere about disconnecting battery 1st before re and re of the TCCM?
Should I have disconected battery 1st? Could I have screwed something up now?

The underhood ATC 20a Fuse was actually blown.
Replaced it...start the Blazer...
4 button display flashes all lights,
then none and the "Service 4wd" light comes on.
Check the same fuse...and toasted again?
Tried again..blew fuse each time.
Can the encoder motor/module, or
TCCM cause the ATC 20a Fuse to blow everytime?
What should I try next?

 

Sounds like your encoder motor has shorted out, causing a high current draw, popping the fuse.

Before crossing that bridge though, have you tested the wiring between the TCCM & the encoder motor? If not, check out the NV236 wiring thread in the Tech Article (DIY) section and run a resistance test from the pin at the TCCM to the corresponding pin at the encoder motor. If that checks out OK, then run a resistance check across the pins corresponding to the large gauge wires on the encoder motor when the encoder motor is cold, then immediately after it blows the fuse when trying to switch mode/range.