2004 Hummer H2 Owner's Manual - Page 168

If the light comes on while you are driving, pull off the road and stop carefully. You may notice that the pedal is harder to push. Or, the pedal may go closer to the floor. It may take longer to stop. If the light is still on, have the vehicle towed for service. See Towing Your Vehicle on page 4-65. Anti-Lock Brake System Warning Light With the anti-lock brake system, this light will come on when you start your engine and may stay on for several seconds. {CAUTION: Your brake system may not be working properly if the brake system warning light is on. Driving with the brake system warning light on can lead to an accident. If the light is still on after you have pulled off the road and stopped carefully, have the vehicle towed for service. That's normal. If the light doesn't come on then, have it fixed so it will be ready to warn you if there is a problem. If the light stays on, or comes on when you're driving, your vehicle needs service. You will also hear a chime sound when the light is on steady. If the regular brake system warning light isn't on, you still have brakes, but you don't have anti-lock brakes. If the regular brake system warning light is also on you don't have anti-lock brakes and there's a problem with your regular brakes. In addition to both lights, you will also hear a chime sound on the first occurrence of a problem and each time the vehicle is shut off and then restarted. See Brake System Warning Light on page 3-33. 3-34