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.

 

You hear no noises at all when pushing the buttons?

Two things I'd be checking first off. Unplug the connectors at the TCCM and encoder motor and look for damaged pins or pins that aren't properly seated. Also check for power at the 4x4 fuse.

 

Looked at TCCM and encoder motor and did not see any damaged or unseated pins. Getting 12.5 volts at the 4wd fuse.

 

See if any info in this thread helps. I'll be checking it out to as this new to me. Ours is a '96 and diff than yours.

https://blazerforum.com/forum/2nd-ge...its-own-52230/

 

Checked out the thread and there isn't anything in it that I haven't already done although I have no idea what the TCEM is. Could it be a typo? Are they referring to the TCCM?

 

TCEM -transfer case encoder motor.

All your replacement parts new? Have any idea what mode the vehicle t/c is in?

 

All parts are new except for the t/c and idk what mode the t/c is in.

 

Where did you get your TCCM? Found this.

1999-2005 GM Transfer Case Control Module Problems Blazer Jimmy S10 Sonoma TCCM Common Problems and Solutions « Auto Parts Cheaper Blog


Just wondering. Why another t/c?

 

Got my TCCM at a place called Patterson's. As for another t/c, thought that maybe it was bound up or damaged inside. Like I said, replaced all the electrical components and nothing seemed to work. Replacing t/c was only thing left to replace.

 

Transfer case mode is probably 2HI as I'm sure you'd feel if it was in a 4WD mode. Especially 4LO. Did it ever work right?

Barring any kind of wire harness damage and taking for granted that all the components you replaced are good,especially the dash switch,TCCM,and encoder I'd be locating ALL the connectors. Get some spray electrical contact cleaner and dielectric grease(any auto parts store). Then spray clean and grease those connectors(male and female sides). Also,I know when I replaced my encoder I had a bit of a problem getting it soilidly flush to the t/c surface. I could have tightened because the gap wasn't very much. Maybe check for any possible binding there. Keep an eye out for any possible wire harness damages to.