Have a 1999 blazer with the 3 button 4wd. When I start the blazer, the lights on all 3 buttons light up (tccm diagnostics i presume.) Then all go out. No lights on any of the buttons. I press all 3 buttons and nothing happens. I replaced all 7 major components (in this order)

1. Vacuum switch
2. vacuum actuator
3. encoder motor
4. TCCM
5. front axle switch
6. the switch on the dash
7. transfer case

Have gone over all the vacuum lines and do not see any cracks or anything that may cause a leak. Pulled the fuses for the 4wd and the ATC for 1 1/2 hours, replaced, circulated the ignition for 5 cycles. Nothing. There's no codes. I have no idea what else to do. I am completely stumped.

 

Wow! Me too. I guess the only thing left is to ring-out the wiring between the switches and the actuator, motor and the TCCM. Good luck and welcome to the forum from another newbie in Kansas!

 

Changed the encoder motor and TCCM twice and still does not work so I gave up on trying to fix my 4wd issue. Removed front drive shaft and is now a 2wd Blazer. Giving the engineers in Detroit the "universal sign" and a few choice 4 letter words too.

 

Mine 4x4 an inside lights didnt work when got it. Turned out curtesy light fuse was blown. Works great now. Why 4x4 would be combined with dome light is just dumb but it is.