1999 Nissan Altima Owner's Manual - Page 127

ANTI-LOCK BRAKE SYSTEM (ABS) (if so equipped) increases wear on the brake linings and pads, and reduces gas mileage. To help save the brakes and to prevent the brakes from overheating, reduce speed and downshift to a lower gear before going down a slope or long grade. Overheated brakes may reduce braking performance and could result in loss of vehicle control. WARNING ● While driving on a slippery surface, be careful when braking, accelerating or downshifting. Abrupt braking or accelerating could cause the wheels to skid and result in an accident. ● If the engine is not running or is turned off while driving, the power assist for the brakes will not work. Braking will be harder. The anti-lock brake system installed in some models controls the brakes at each wheel so the wheels do not lock when braking abruptly or when braking on slippery surfaces. The system detects the rotation speed at each wheel and varies the brake fluid pressure to prevent each wheel from locking and sliding. By preventing wheel lockup, the system helps the driver maintain steering control and helps to minimize swerving and spinning on slippery surfaces. rapidly applies and releases hydraulic pressure (like pumping the brakes very quickly). While the actuator is working, you may feel a pulsation in the brake pedal and hear a noise or vibration from the actuator under the hood. This is normal and indicates that the anti-lock system is working properly. However, the pulsation may indicate that road conditions are hazardous and extra care is required while driving. Self-test feature The anti-lock brake system is sophisticated, with electronic sensors, electric pumps, and hydraulic solenoids controlled by a computer. The computer has a built-in diagnostic feature that tests the system each time you start the engine and move the vehicle at a low speed in forward or reverse. When the self-test occurs, you may hear a ''clunk'' noise and/or feel a pulsation in the brake pedal. This is normal and is not an indication of any malfunction. If the computer senses any malfunction, it switches the antilock brake system OFF and turns on the ABS brake warning light in the dashboard. The brake system then operates normally, but without anti-lock assistance. If the light comes on during the self-test or Using the System Depress the brake pedal and hold it down. WARNING Do not pump the brake pedal. Doing so may result in increased stopping distances. Normal operation The anti-lock brake system does not operate at speeds below 3 to 6 MPH (5 to 10 km/h). The speeds vary according to road conditions. When the anti-lock system senses that one or more wheels are close to locking up, the actuator (under the hood) 5-18 Starting and driving