Wow, I feel half retarded. Went under the blazer today to check my connections to the encoder/transfer case area. I immediately notice that something is wrong, big time and guess what.....

THE FRONT DRIVE SHAFT IS GONE as WELL AS the ENCODER motor.

I have nothing there at all. Two connections, 4 pin and a 6 pin just dangling. NO drive shaft, no encoder motor. I got this "as is" from a local dealership last week. They told me upfront that the 4wd wasn't working.

Now, I wonder if they even knew what was actually missing. Jeeze. So off to find a front drive shaft and encoder motor.

Do I have to clear the TCCM codes first prior to installing the new encoder/shaft?

 

Guess it's time to go to the junk yard/salvage yards and find a front drive shaft and encoder motor.

 

Ok, I have a used front drive shaft and encoder off of a working 2000 Blazer with the 4 button switch and matching transfer case etc.

Is there a particular order I have to install these in, obviously easier to install encoder motor first then drive shaft. I have to put a new u-joint in the front drive shaft. (figured since its off of a used blazer, might as well replace it while I have it off)

Should I disconnect the negative terminal/pull ATC fuse and then install? Or is that necessary?

 

Disconnect the battery negative and then go through the install. It is easier to install the encoder motor and then the driveshaft.

 

Should I put some dielectric grease inside the connections of the encoder as well?

Thank you for the response.

 

Ok...

I disconnected the negative terminal, hooked up the encoder motor. Installed the front drive shaft with the new u-joint. Reconnected the battery and fired it up.

All lights on the 4wd switch, flashed and then stayed lit on 2wd. I took it out in the country for a test drive. About 2 minutes into the drive the 4wd auto light flashed and then stayed on. Then while 4wd auto light was on solid, the 4lo light began to flash. I pulled over, pushed 2hi and it stayed on again. At the stop sign, the light flashed by itself again and went into 4wd hi.

I got it back into 2hi and drove it home. Previously, I had rewired the connections to the switch, because someone had already done it once previously, due to shrink wrap around splices. When I moved the wires I could make the lights go on and off. So it was rewired properly and I was still having the switch issue.

I knew the encoder motor was good, because it was out of a 2000 working 4wd 4 button system. I had also taken the TCCM out of my dad's part 2000 blazer, so I had a spare. I figured since the switch was replaced, rewired. Newer encoder motor and drive shaft that my issue was with the TCCM. Reasoning: Even after installing the encoder and drive shaft, I was still hearing a series of clicks coming from the TCCM.

So I get it back in the garage, disconnect the negative terminal. I then swapped out the TCCM with the one from the 2000. Hooked it all back up and it's been running like a champ since. No clicks, all buttons work when I want them too. So I took it wheeling for the first time and it was golden.

What an ordeal. Well I am happy to say it's fully functional and I have a new problem to fix. The temp. door actuator motor.

 

The switch tells the TCCM which gear to be in based on resistance. It sounds like you have something causing the resistance between the TCCM and the switch to change, causing the change in gears. You can test the switch pretty easily. You should also test the wires that are responsible for completing the circuit to/from the TCCM through the resistors in the switch.