Hey guys, I have a 2000 Blazer with the 4 button switch and the 236 transfer case. I just bought it recently and the 4x4 doesn't work. None of the indicator lights work and I hear no clicking when I push the buttons. I checked the fuses, tried using a new push button switch, and tried taking the fuses out for 15 minutes and cycling the ignition on and off 5 times to no avail. Also, the lights light up for a split second when I turn the ignition on but then they stay off. I'm wondering if it sounds like a wiring issue or if it could maybe just be a bad tccm. I disconnected the tccm and I didn't see any corrosion. Any thoughts ?

 

You should run through all of the wiring and test for proper continuity to the various components as well as proper power & ground.

Does the service 4wd light come on?

 

No, the service light isn't on.

 

I found a tccm at a local junkyard and replaced mine. The buttons light up and the unit clicks now but it goes right back to 2 hi. Looks like I have a vaccuum problem or a bad encoder motor now. I'm just happy to have it light up and click now, at least I know it's getting power.

 

I have a 99 Blazer and I had the exact same problem with it only going to 2hi I had to plug the hose that comes up to the hood to the vaccum ball with a srew and I also had a vaccum line off at the sensor mounted under the lip by the cowl panel around the center of the truck. Hope that helps. If neither of those work then you can always check the front diff. actuator under the battery and battery tray on the passenger side

 

I checked the vacuum switch and the actuator and they're both ok. which line are you talking about that you had to put a screw in and where was it supposed to be connected to ? Since my last post I've been messing with the buttons on the switch and after I hit a couple buttons the tccm clicks and the lights go out on the switch and nothing works until I unhook the battery for awhile. Now I'm confused again, I'm not sure if it's another tccm problem with the new unit or if it's something else

 

4x4 is fixed !! Turned out to be the tccm and the tcem, replaced them both and it works perfectly now