2005 Chrysler PT Cruiser Owner's Manual - Page 212

212 STARTING AND OPERATING If either of the two hydraulic systems lose normal capability, the remaining system will still function with some loss of overall braking effectiveness. This will be evident by increased pedal travel during application and greater pedal force required to slow or stop. In addition, if the malfunction is caused by an internal leak, as the brake fluid in the master cylinder drops, the brake warning indicator will light. Anti-Lock Brake System (ABS) - If Equipped The ABS gives increased vehicle stability and brake performance under most braking conditions. The system automatically "pumps" the brakes during severe braking conditions to prevent wheel lock up. All vehicle wheels and tires must be the same size and tires must be properly inflated to produce accurate signals for the computer. However, the system will compensate when the compact spare is in use. During stops where ABS is activated, a vibration of the brake pedal may be felt and associated system noises may be heard. NOTE: Pumping of the brake pedal will diminish the effectiveness of Anti-lock brakes 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.