I have a problem only with 4-wheel Low?

STEVE620

MEMBER
2007 GMC ENVOY
4.2L
6 CYL
4WD
AUTOMATIC
190,500 MILES

I do not use my 4-wheel drive except for snow that we just had. I think I have a problem only with 4-wheel Low going forward. When I engage it seems like it's slipping at first, I can see hear it then works like I think it should. Backwards no problem and there is a big difference going backwards. I dropped it off at dealership and they told me it's working flawlessly I still have my doubts, what do you think before I take it elsewhere also before I took it in the dash light with the wrench and 4D service light was on and of course the light was out. And while driving it in the snow the selector knob light would not change until I would restart engine. Sorry if I'm all over the place here but as I remember I'm typing.
Thank you

7 Replies

KEN L

MASTER CERTIFIED MECHANIC
42,968 POSTS

Hi Steve, with the wrench light on it should have trouble codes stored. let's go over this guide to retrieve the codes:

https://www.2carpros.com/articles/checking-a-service-engine-soon-or-check-engine-light-on-or-flashing

To me it sounds like the transfer case encoder motor is getting weak and not commanding the shift fork inside. Here is how to change it out. Check out the images (below). Please let us know what happens.

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Wednesday, January 24th, 2024 AT 12:26 PM

STEVE620

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I just used a code reader and I'm not getting any codes.

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Thursday, January 25th, 2024 AT 6:49 AM

KEN L

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Okay, I know a weak encoder motor can cause the transmission case not to shift correctly but I have also seen internal damage to the transfer case cause this problem as well. You might be able to remove the encoder motor and shift the transfer case by hand, or you can activate the motor once it is out of the case to see how it responds.

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Friday, January 26th, 2024 AT 10:40 AM

STEVE620

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60 POSTS

Right now, the 4-wheel drive is working. When this first started to happen, I checked it with a code, and I just remembered the code I got was P0650.

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Friday, January 26th, 2024 AT 1:56 PM

KEN L

MASTER CERTIFIED MECHANIC
42,968 POSTS

The P0650 code in a 2007 GMC Envoy is a diagnostic trouble code (DTC) related to the vehicle's Malfunction Indicator Lamp (MIL) control circuit. This code indicates that there is a malfunction in the control circuit of the MIL. So, I don't think this will cause an issue with the 4wd. Does the check engine light come on with the key?