2009 Jeep Grand Cherokee Owner's Manual - Page 312

310 STARTING AND OPERATING wheel lock-up and help avoid skidding on slippery surfaces. All vehicle wheels and tires must be the same size and type, and tires must be properly inflated, to produce accurate signals for the computer. The ABS pump motor runs during the self-test at 12 mph (20 km/h) and during an ABS stop. The pump motor makes a low humming noise during operation, which is normal. WARNING! • Pumping of the Anti-Lock Brakes will diminish their effectiveness and may lead to an accident. Pumping makes the stopping distance longer. Just press firmly on your brake pedal when you need to slow down or stop. • The ABS cannot prevent the natural laws of physics from acting on the vehicle, nor can it increase braking or steering efficiency beyond that afforded by the condition of the vehicle brakes and tires or the traction afforded. (Continued) WARNING! Significant over or under-inflation of tires or mixing sizes of tires or wheels on the vehicle can lead to loss of braking effectiveness. The ABS conducts a low-speed self-test at about 12 mph (20 km/h). If you have your foot lightly on the brake while this test is occurring, you may feel slight pedal movement. The movement can be more apparent on ice and snow. This is normal.