Chevrolet 1998 Express Van Owner's Manual page 170

Anti-Lock Brakes (ABS)
Your vehicle has anti-lock brakes (ABS). ABS is an
advanced electronic braking system that will help
prevent
a
braking skid.
When you start your engine and begin to drive away,
your anti-lock brake system will check itself. You may
hear a momentary motor or clicking noise while this test
is going on. This is normal.
ANTI
-
LOCK
United States Canada
If there's a problem with the anti-lock brake system, this
warning light will stay on. See "Anti-Lock Brake
System Warning Light" in the Index.
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. 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.