93 gmc jimmy s15 4x4 cpi
i've read the other post but my 4x4 switch doesnt even light up. It did before but and now it doesnt. I unplugged the tccm, checked the fuse, and nothing helped. I tried to do the diagnostic and when i jump the a&j pins nothing happened. Is there a relay or something that i am not thinking of.

 

Did you try turning the driveshaft by hand after pushing the button?

Does the vacuum going to the front axle work when you try to engage it and is the front axle engaging?

I am not familiar with the electronic shift 4x4 on these vehicles.

 

If your buttons don't light up, you likely have a power/ground or other wiring issue to/from the TCCM. You need to check all connections,test continuity on all wiring from one connector to the other, and test for proper power/ground on the applicable wiring. The diagrams should be in one of the NV233 threads in the Tech Article (DIY) section.

If the buttons aren't lighting up, testing the mechanical system really won't get you anywhere.

 

When I first started diagnosing my 4x4 issue, I had no lights either. My TCCM was bad. Got a used one from a junk yard and it was good to go. Until about 7-8 months later when the TC control motor went out

 

Thanks guys. Im gonna try to get a tccm from a yard and then ill look at the continuity