I have a 2000 Blazer with 4 button 4x4. My 4wd has always worked good until a month ago when it got stuck in 4hi. My mechanic scanned it and said it had a high voltage code and replaced the motor with a new Dorman one.

It worked good for about 2 days and got stuck in 4hi again. This time it gave a low voltage code. So my mechanic checked all the wiring and also checked the 4x4 computer plug for corrosion. Everything looked good, so he replaced the 4x4 computer. No luck. So we put on Dorman motor number 2.

Worked good for one weekend, got stuck in 4hi again. Motor position error code this time. Next he put in a A1Cardone motor.

Right now I can shift into 4hi or low with ease, but it will not go into 2hi unless I stop the car, turn it off, then if I turn the ignition switch to "on" and then push the 2hi button, then it will go into 2hi.

My mechanic refuses to do any more work on my Blazer until I buy a GM made encoder motor ($430) because he is saying that all the aftermarket ones are junk. I cannot believe that 3 aftermarket motors were all bad. I have read dozens of threads on similar problems, but not one exactly the same as mine. I would appreciate any help or advice anyone could give.

My mechanic has ruled out the transfer case because he says you can easily shift between all modes manually.

 

Beyond testing the wiring & dash switch, a scan tool capable of bi-directional control is necessary to see exactly what is going on in the TCCM.

Have you tested all of the wiring (ohm'd it out from every connector to the opposite connector between the switch & the TCCM as well as the TCCM & the encoder motor? Have you checked all of the main power & ground wires to the TCCM & Encoder? Have you tested the switch in the dash for proper resistance read-out from the TCCM connector?

Wiring diagrams for the NV236 transfer case are found in the Tech Article section as are the resistance specs for the switch.

 

All wires between encoder motor and TCCM were checked. Wires leading to TCCM were checked. TCCM was changed without any difference in operation. Dash buttons were changed without any change in operation. So far I owe my mechanic a lot of money in diagnostic time.

 

Why did he change those items? Everything (but the wiring) has been changed with no change in the response of the system... Sounds like you need a new mechanic...

So what have YOU done to diagnose the problem? Have you just been taking your mechanic's word that things have been checked?

Do YOU have a DMM (digital multimeter)? If so, time to sit down with the wiring diagrams available on this site and use it. If not, even a simple DMM can be picked up at Walmart for $30 or so.