99 Suburban-"Service 4WD" Light

[cyoung]

I've been using the 4wd for several days in the snow. Worked fine til yesterday AM when I started it up and the "Service 4WD" light came on. I couldn't get it in 4 hi or low or 4wd auto. 2 wd only. I drove it that way during the day then when I started it up to come home it had put itself into 4wd auto and I could not get it back into 2 wd. Any syuggestions where to start trouble shooting this?
Thanks!

 

[cyoung]

Sorry for the double post! Now I cannot see how to delete one of them.

 

[Lee]

Encoder most likely, it will get trash on it and act as you described

 

[cyoung]

Encoder most likely, it will get trash on it and act as you described

Is there any easy fix? I'm not sure where the encoder is located either.

 

[Fabrik8]

The switch, encoder, motor, and module are all common problems. Get the codes scanned and see what the codes say.

 

[Fabrik8]

This is a different year, but will likely either be the same or similar enough to see what you're getting in to if you DIY it.

Encoder Motor Replacement - Z71Tahoe-Suburban.com

 

[cyoung]

Well if it is the encoder motor, the replacement sounds pretty simple. Thanks for all replies.