ABS light strange behavior

[yuk]

'96 Yukon, SLT 2 door. 350 Vortec, 140K.

The ABS light comes on after moving forward a few feet just after startup. I hear a small grinding sound, maybe coming from up front somewhere. Happens everytime EXCEPT when in 4wheel Hi. I can change into 2Whl after say 5 secs of forward motion, and the ABS light will not come on. The only time ABS light appears is if I start out in 2Whl.

I realize there are codes, but they want 50 smackers just to tell me what they are. I'm wondering if someone here has insight into what these clues could indicate. Thanks.

 

[SunlitComet]

it is best to remove the front abs sensors first and check for contamination first. There is a method to possibly pull abs codes yourself. I believe it was grounding wire the tan/white wire on the dlc connector to ground, turn ignition on and read abs light flashes. at your own risk since you are a 1996 model. report back any codes hear.