Hello all
I'm new here so please don't hold that against me! I hope there is a 4wd mechanic on this forum. I am going to give as much detail as I can in the hope of getting this fixed. A little old lady wanted me to find her a 4wd car for this winter. I found a nice clean 2000 Jimmy for her at a local auction. While cleaning it up and servicing it, I discovered it was stuck in 2hi. I replaced the vacuum switch and all the hoses (more on that later). When I try to engage the 4wd, all that happens is the control module in the right kick panel chatters and the lite in the switches blink 4 times and goes back to 2hi . OH yea it is a 3 switch setup. Pulled the encoder/shift motor assembly to make sure it works. While I had it off I grabbed the shift nub sticking out of transfer case and gave it a turn counter clock wise to make sure it was capable of shifting . All seems good there. Returned it back to original position and re installed the encoder assembly. I found a wire in the encoder plug had a bad terminal on it and repaired (hoped that was the problem). Put it all back together and the same thing happens. Replaced the module in the right kick panel.No change. Decided to check the fluid level in transfer case and it was way over full. Is it possible the encoder/shift motor is too weak to shift the transfer case? Or somehow be out of phase and can't shift it?

Now onto the vacuum lines. I checked the actuator under the battery and there is no vacuum present. But if I use my vacuum pump the diaphragm works fine, My question here is there a good vacuum diagram available that shows where the vac goes to on the switch and routing to vac actuator? I have good vac off my intake but from there it looks like someone has messed with it.

I hope this gives someone the info they need to help me and thanks for reading this



Update: I found the vacuum line diagram I need (still going thru previous posts).

how do you pull the DTC codes for the 4wd?