Good morning all. Looking for a little advice. I mjust replaced my tranny on my '01 ZR2 Blazer. Went off without a hitch as they say. My problem now is. My service 4wd light comes on. I turn the key on and off about 5 x's and it clears. I start it and put it in any selection. It will engage and soon after the service light will come on. When I do engage auto, 4hi/lo. I hear the motor and the computer in kick panel working as i engage. Any advice will help. I'm sure theres a thread on here, but caouldn't find what i was looking for. Thanks. I have the 4 button with Auto

 

Is your 4 wheel drive working like it should? Just the service light coming on for no reason that you can tell... I have a 98 Blazer but it has the 3 button switch...

 

With the 4-button system, diagnosis starts with reading the TCCM codes which will require something more than your basic scan tool. Sure, there are things you can check (vac system - engine to solenoid to actuator, actuator cable movement - should be ~3/4", TCCM connector condition - no corrosion, etc.), but it is best to start with what the vehicle is trying to tell you is malfunctioning.

 

A little more update.
I cleaned the connections to tccm, but still nothing. Went to salvage yard and borrowed another tccm and same result. Put original back in. Now light is on all the time and no lights on the switch. I can here the tccm clicking when I turn the key. Yes I did disconnect battery when doing install. Could it be that the switch it bad. Wierd thing is. Everything worked fine before I replaced my tranny. Will have to get underneath and check connections on tcase. Any other ideas. Thanks again.

 

The switch can be tested with a multimeter; details can be found in the Tech Article section.

 

Another update.
the local salvage yard was nice enough to let me borrow several parts for my elimination.
TCCM-good
Selector button switch- good
Vacuum switch- good
Found that the encoder motor wasn't up to snuff.
Purchased and installed new one. Everything works, but when I drive about 100yrds engaged in 4h or auto. My service light comes on and transfer case disengages what is selected. All my electrical connections are good and clean. I disconnected the battery overnight. Will see what happens today. Any ideas of what I may have missed. Also. I can't get the transfer case to go into neutral not that it matters

 

I believe I have found my problem.
A few of the terminals in the big plug block to the TCCM were pushed out of there locks. This may have been caused from the corrosion and unplugging and plugging back in. Going to pull each terminal and clean thoroughly. Thanks for all the help everyone.

 

It is always great when someone reports back saying "fixed it"