02 ZR2/ 3 button

Got our first real snow (6”) in a couple of years in my part of the world and no 4WD. Just for kicks I test about once a month just to make sure it engages. I have searched and found many threads on the subject but non that really seem to fit my scenario.

While in drive, complete stop and rolling, push 4hi and nothing happens, no lights nothing. In neutral, push 4hi and the 4hi and 4low lights flash 5 times and goes back to 2hi. Still in neutral, push 4low and the light blink a couple of times and engages and works like it should (I think), Crab’s during sharp slow turn on dry.

All I have done to this point is confirmed vacuum to actuator and pulled a vacuum (Mighty Vac) to the actuator while in park, neutral and drive while pushing 4hi button......nothing.

Thanks in advance for your help.

 

My first suggestion that is free and easy: take the 4wd switch assembly out, disconnect, separate housing, reflow solder connections. May/ may not help....but worked on mine.
2nd free: check/clean connectors at TCCM.

 

Thanks Lanny.....please excuse my ignorance but.....TCCM? Transfer case control modual? Location?

 

Yep on the TCCM....location is at front passenger floor, below the dash, next to the door. It is behind the trim panel....which just pulls off. Probably a video on YouTube about......have not looked.

Appears you have 4Lo, so encoder motor is working...just not for 4Hi.

Good Luck.

 

FIXED!!! ECM reset did it. Wish I would have started with that. Since I already replaced all vacuum lines, actuator and TC switch I back tracked those first and replaced dash switch I had laying around. Next time I will know where to start.

 

An ECM reset??....that does not make sense to me. As far as I know the ECM has zero control with 4wd operation....just engine.

 

Glad it's working for you. It really sucks when no 4WD happens when it snows! Speaking from experience. Defeats the purpose of driving the vehicle the rest of the year.

For the record (and to help others understand), can you please describe what you did during your ECM reset? Also, did you take a look at any of the connectors on the TCCM?

 

Very possibly used the wrong term "ECM reset". Disconnected the battery for 30 minutes. Sorry for the confusion. Did not even look at the TCCM, that was going to be my next step.

 

Yeah, guess that is really a vehicle reset. But anyways.....so 4Hi/4Lo are correctly working now? Goes into both modes no problems?

 

Everything works as it should now except for the loss of vacuum in the HVAC system that will cause the front diff to disengage when under a heavy load. I am going to solve that issue when the motor comes out this spring with the cable pull for front diff.