2005 Jeep Liberty Owner's Manual - Page 247

STARTING AND OPERATING 247 ANTI-LOCK BRAKE SYSTEM - IF EQUIPPED The Anti-Lock Brake System is designed to aid the driver in maintaining vehicle control under adverse braking conditions. The system operates with a separate computer to modulate hydraulic pressure to prevent 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 Anti-Lock Brake System conducts a low speed self-test at about 12 mph (20 km/h). If for any reason, your foot is on the brake when the vehicle reaches 12 mph (20 km/h), this check will be delayed until 25 mph (40 km/h). The Anti-Lock Brake System pump motor runs during the self-test and during an ABS stop to provide the regulated hydraulic pressure. The motor pump makes a low humming noise during operation, this is normal. During off-road use, loss of traction can temporarily defeat the system and cause the warning light to illuminate. Turn the ignition OFF and ON again to restore Anti-Lock Brake System function. 5 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.