Encoder for 2002 GMC Envoy Problem

[vinniegambini]

I'm on vacation and my "Check 4WD" light came on. You could turn the knob but the light would stay on 4WD. Took it to dealership and they said my encoder motor was bad. They replaced it but now they are saying "encoder motor will still not run. No codes module receiving switch input but no motor control output. Module shorted by motor." They wanted to charge me another $300+ to fix module and wait a day for the part. I'm going to take it back home for my dealership to look at it. Can anybody give me any other course of action to take or ideas? I'm almost thinking new encoder motor could be bad. :undecided

[the roadie]

Welcome! I moved this to the 4X4 drivetrain forum for the best exposure. It's also my specialty system.

You say you were in 4HI mode? Were you offroading at all to have the switch in 4HI?

And then you moved the switch to 2HI, and it stayed lit on 4HI? Did it flash or make any indication that it knew you had moved the switch to 2HI?

The control module is pretty well designed, and the encoder motor should blow a fuse if it's shorted internally or otherwise refuses to work. But I can't see why the dealer would diagnose the problem, change a part, and then say the part THEY CHANGED was bad and took out your control module and they have no responsibility!!! :hissy:

Time to escalate it to GM regional if you get no satisfaction with a call to the service manager. That's true BS.

If you were nearby, we could spend a couple of hours carefully exchanging parts until we knew which one was bad. You can also take it back to your own local dealer. Or you can demand satisfaction from the poor diagnosticians at the dealer who put in the poison encoder motor.

Do you have the encoder motor they took out? You need that.

Are any lights flashing on the mode selection switch as you change from morde to mode? You aren't locked in 4WD mode now are you? Difficult to drive on pavement that way.

[vinniegambini]

No I was not offroading at all. I saw the Check 4WD light come up but I then looked down and saw the light was on 4WD but the switch was in the 2hi mode. I moved the switch around but the light would not change out of 4wd. They used the diagnostics and that's what came back as a bad encoder. Now the module won't work which I assume relays the info to the transfer case. Correct me if I'm wrong. I was guessing that maybe the new part they put in was bad. They didn't say that. I'm trying to think of everything. I do have the old encoder motor and will give that to the dealership when I get home. The dealer in SC said it is in 2HI and won't come out since no signal is being sent. I will only hope for the drive home to MD.





Welcome! I moved this to the 4X4 drivetrain forum for the best exposure. It's also my specialty system.

You say you were in 4HI mode? Were you offroading at all to have the switch in 4HI?

And then you moved the switch to 2HI, and it stayed lit on 4HI? Did it flash or make any indication that it knew you had moved the switch to 2HI?

The control module is pretty well designed, and the encoder motor should blow a fuse if it's shorted internally or otherwise refuses to work. But I can't see why the dealer would diagnose the problem, change a part, and then say the part THEY CHANGED was bad and took out your control module and they have no responsibility!!! :hissy:

Time to escalate it to GM regional if you get no satisfaction with a call to the service manager. That's true BS.

If you were nearby, we could spend a couple of hours carefully exchanging parts until we knew which one was bad. You can also take it back to your own local dealer. Or you can demand satisfaction from the poor diagnosticians at the dealer who put in the poison encoder motor.

Do you have the encoder motor they took out? You need that.

Are any lights flashing on the mode selection switch as you change from morde to mode? You aren't locked in 4WD mode now are you? Difficult to drive on pavement that way.

[the roadie]

If the switch is in 2HI and the light is in 4HI (there is NO "4WD" light, only "A4WD" "4HI, and "4LO") then the problem MUST be in the switch, wiring, or the control module.

It's flat out IMPOSSIBLE for a bad encoder motor to force the switch to display a 4HI light when the switch is in the 2HI position.

The service staff is incompetent or lying if that's their diagnosis given those exact observations. Unless there's something else they saw that you didn't.

I also can't think of a way that a bad encoder motor can affect the relationship of the switch to the control module.

You need a competent and honest diagnostician. Hope your hometown dealer has one. That encoder motor is going to be evidence you need for your complaint letter to GM and the servicing dealer - guard it carefully.