Stuck in 4wd Low!

[paullie]

2001 Blazer

On the way home from work last night, the 'service 4wd' light came on then went off, while it was on, I noticed the '4wd low' light on the switch panel was flashing. It stopped when the service light went off . I got home and my wife took the Blazer to the store, when she pulled out of the driveway at the store it went into 4wd low and stayed there.

I read many many of the helpful threads here to attempt to troubleshoot the problem.

I changed the transfer case fluid (GM is proud of that stuff)

I removed the battery and battery tray to check the front diff. vacuum actuator and noticed that it didn't seem to be engaged fully in either direction. I connected the battery back up and it engaged fully (exposing a clean section of cable). This leads me to believe that the control solenoid AND the actuator diaphram are working correctly.

I tried removing the front diff sensor(saw that in another post) to try to get it to default back into 2wd. no dice.

I did notice that upon reconnecting the battery that it sounded like an electric motor under the car cycled back and forth then stopped. I'm assuming this is the shift control motor. Since it's making noise, i'm going to assume that it is at least functioning somewhat properly.

What we're left with (unless i'm missing something) is that the encoder located in the passenger side kickpanel is bad. I suppose what I'm asking is that before I go plunk down some coin on a new encoder module, that i've covered all my other bases.

Thanks for any help.

[BlazerLT]

Sounds like something is trying to engage the encoder motor without your input.

Check wiring going to the transfer case encoder motor which is on the transfer case, not on the kickpanel.

[paullie]

OK. I'll give that a whirl. Following your train of thought, what's the possiblity that the gear selector switch itself is malfunctioning? Seems that a false signal from the switch could cause that as well.

[BlazerLT]

Now you are thinkin.