I have a 2000 GMC Jimmy with the 236 transfer case and the 4 button 4X4 switch on the dash.
So let’s start from the beginning; a while back the 4X4 switch lights were acting strange…blinking when going into 4hi and then going back into 2hi, but after pushing the button a couple of times it would work fine and go into 4hi. Then it stopped working and would only go into 2hi or 4low.
Back then I took out the Battery and checked the Vacuum Actuator and Cable for the Front Differential, and after finding a vacuum line that was off to the vacuum solenoid on the firewall everything was fine again.
Then a couple of weeks ago I decided to do annual maintenance and change the transfer case fluid. Afterwards I went on a short road trip to get the new fluid worked into the various gears and when I put it into 4low it would not come out, and the lights on the dash went out for the 4X4 switch.
Since then I have replaced the 4X4 Dash switch, the Transfer Case Encoder Motor (the transfer case is now back in 2 hi) and the Transfer Case Control Module but the lights are still not working on the 4X4 Dash switch.
My question is; does something need to be reset in order for the lights to come back to the dash switch? Even when I turn the key over to start the truck, the lights do not blink.

Any advice is appreciated.

Thanks,
John

 

Are you sure that the new (replaced) transfer case control module dash switch was working before you fitted it?

 

Thanks DRG, all of these parts were brand new when I installed them. I hoped that they were in working order.

 

Take a look here: http://www.rlfarms.com/blazer/4button/

The left picture...

I believe the B and C connections on the 4x4 switch feed the "electronic logic" in the switch to control the brightness of the LEDs. If you need info as to the source of "B & C" let me know and I'll get the shop manual out again, and pass along any info I can glean from it....... I believe one line is 12 volts, and the other one is a variable voltage from the dash light dimmer, but that's just off the cuff and memory from a few weeks ago when I fixed my encoder.....

to see my "fix" for my flakey encoder see: http://RLFARMS.com/blazer/

Good Luck

 

Not to be overly simplistic, but did you check the fuses? It's possible that somewhere in all that you popped a fuse.

 

John,

After rereading your OP, I believe your trouble started with a flakey encoder (switch) on the TC shift motor. The mode of only having 2-hi and 4-low is a "fail soft" mode the TCCM goes into when the encoder "feedback" is flakey and/or does not match what the TCCM expected to "see". Removing the battery will "clear" the TCCM from the "failure mode" temporarily, only to go back into that mode after a couple of times switching to 4wd and the flakey encoder "data" to the TCCM. Mine would shift fine several times after a power down & up of the TCCM. It took figuring out how the encoder works (in relation to the TCCM) to fix mine...

 

I just popped my abs switch out and put the new one in place and the light worked again on mine.

 

I figured out that it was bad wires at the TCCM. I'm debating whether I want to find another Harness for the TCCM, or just leave it stuck in 2Hi.
I was also considering whether I should just make a manual linkage and bypass the TCCM all together. Anyone know of any floor shifters out there that would work?

Thanks for the advice Fred, that diagram was helpful.

 

Do you need the pinout / wiring diagram for the TCCM Harness?? It seems ashame to "modify" the truck for manual 4x4.... I do understand the desire for a manual transfer case shifter though... I wish that was an option on my 2011 Silverado, but unfortunatly the "kids" that are designing (and buying) the newer 4x4s are the "pushbutton" generation, and wouldn't know how to use a rotory phone.........

If you need any info from the GM shop manual let me know.... Good Luck....

 

Thanks Fred. I found it earlier. I hate wiring. Working on it now.
Thanks,
John