I have a 2005 GMC Sierra extended cab, and when I break I feel the ABS coming on. I have had it into a garage a few different times, and they can't seem to figure out what the issue is. Also my service four wheel drive light keeps coming on, they also can't figure out why this is on.

Anyone had this issue or know why this is happening or if it is serious?

-Bella

. Check for ABS codes.

. Clean each wheel's ABS Sensor.

. Change the brake fluid with an ABS-approved fluid every 2 years.

Wouldn't mechanic have cleaned the sensors? And what do you mean check ABS codes?

Your guess is as good as mine whether he inspected and cleaned the ABS Sensors. ABS Code Readers can determine if any ABS codes have been thrown. My advice is to take it to your GM truck dealer for servicing.