2007 GMC Acadia Owner's Manual - Page 335

But you will use it when you brake. Once the power assist is used up, it can take longer to stop and the brake pedal will be harder to push. Adding non-dealer/non-retailer accessories can affect your vehicle's performance. See Accessories and Modifications on page 385. Anti-Lock Brake System (ABS) Your vehicle has the Anti-Lock Brake System (ABS), an advanced electronic braking system that will help prevent a braking skid. When you start the engine and begin to drive away, ABS will check itself. You might hear a momentary motor or clicking noise while this test is going on, and you might even notice that the brake pedal moves a little. This is normal. If there is a problem with ABS, this warning light will stay on. See Anti-Lock Brake System Warning Light on page 223. Let us say the road is wet and you are driving safely. Suddenly, an animal jumps out in front of you. You slam on the brakes and continue braking. Here is 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 wheel. 335