1998 Chevrolet Astro Owner's Manual - Page 191

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. 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 ateach front wheel and at both rear wheels. ANTI LOCK 4-7