So far: I am having with my 2001 Blazer. The push button switch will flash when 2wd is pressed but always defaults to 4hi. it will also "appear" to go into auto 4wd but the front axle is certainly still engaged as it barks going around tight turns. My instrument panel switch cycles properly when I turn the key on (all lights come on for a sec and then lights 4wd only).....so I think that eliminates that switch maybe?? I found a vac hose cracked and nearly off...Eureka!!....nope no change. diaphragm and cable seem to be working fine, other than the vacuum remains on the diaphragm, not allowing it to go out of 4wd. I have learned that 99 and up have electric switch is located center rear under the hood......I assumed my is working as there's vacuum there. When I press the 2hi button the encoder motor on the TC, tic's for a few sec's stops and tries again, then defaults to 4 hi again. I think that means the encoder motor is too weak to make shift positions. I've pulled it off and am headed to wreckers soon. From my research, I think the encoder motor for Blazers 99-2005 are all the same regardless if they are 3 button(2wd, 4hi and 4 lo) or 4 button (2wd, 4hi, 4 lo and auto 4x4) dash switches. mine has 2 electrical plugs, one is 6 pin screwed right to the motor (opposite side and opposite end) and the other is a 4 pin pig tail that comes from the base of the plastic cylinder. Can anyone confirm that is true? Also, am I headed down the right path or am I "blow'in sunshine"?!?


thanks

 

I would have tried to clear the codes from the TCCM first and see if it fixed your issue (remove tccm fuse from under dash for 3 minutes then put fuse back in and cycle the key on and off 5 times, DO NOT START THE TRUCK WHILE DOING THIS) When cycling turn key on until 4wd lights go out, start the truck and see if it is working correctly.

As for the right encoder motor, am not sure about that one.

 

I figured the TCCM was doing its job, calling the encoder motor to shift. When I heard it ticking and trying to shift.

 

You mentioned your encoder motor has 2 electrical plugs. My 2000 3-button has only one electrical connector. For replacement parts and troubleshooting specify which one you have. The 3 and 4 button systems are very different.

 

My systems is 4 button: 2Hi, 4Hi, 4 Lo and auto 4x4

 

I understand, but I have seen many times on this forum of people having issues like this and pull the TCCM fuse for 3-5 minutes, then putting it back in and cycling the key on and off 5 times fixing the problem.

 

So I jacked up all wheels and put in drive. selector says 4Hi is on and all 4 were rotating, however I was able to stop either front wheel be wedging my boot against the sidewall of the tire. I had my wife stop the front wheels while I looked at the front drive shaft. It was still spinning even when the front wheels were stopped.


Is this from the front differential only trying to engage and I am seeing the "drag" from the gears not meshing?? I don't hear any sounds coming from the front diff indicating any problems. I'm going to fiddle with the vac actuator cable again to see if there's any change.


Any input on this would be much appreciated.


2001 Blazer with auto 4wd

 

I have the same issue on my 2001 4wd. Hi and auto work but lo just keeps blinking.

I had a mechanic look at it and he said the cheap parts(vaccum, switch, actuator) are fine so it might be either internal or the 4wd motor thats causing the problem. I didnt bother fixing it.

I just bought a 2002 4wd as well a week ago and the lo on that one keeps blinking too..

 

Just making sure that you know you have to be in neutral to shift it into 4lo, right?

 

If the front shaft is moving and the front wheels are moving but you are able to stop them from spinning that easily, it sounds like the front diff is not engaging all the way.
Vac issue..