GMC 2001 Envoy - Manual (Page 225)

4-9
Here’s how anti - lock works. Let’s say the road is wet.
You’re driving safely. Suddenly an animal jumps out
in front of you.
You slam on the brakes and continue braking.
Here’s what happens with ABS.
A computer senses that wheels are slowing down.
If one of the wheels is about to stop rolling, the
computer will separately work the brakes at each
front wheel and at both rear wheels.
The anti - lock system can change the brake pressure
faster than any driver could. The computer is
programmed to make the most of available tire and
road conditions. This can help you steer around the
obstacle while braking hard.