Antilock Brakes / Traction Control Systems: Description and Operation
INTRODUCTIONThis section deals with the complete diagnosis and services for vehicles equipped with rear wheel anti-lock.
SYSTEM DESCRIPTION
The system monitors rear axle rotation during braking; if axle speed decreases at a rate that indicates rear wheel lock-up, the system adjusts hydraulic pressure to the rear brakes.
he system is designed to minimize rear wheel lock-up under severe braking conditions or when traction is reduced due to slippery roads. Under normal operation, the vehicle braking system will function like a conventional braking system.
The RWAL system works only when the brake pedal is applied and possible lock-up conditions exist. It cannot cause the brakes to be applied without the pedal being pressed.
Normally, the driver cannot tell when the RWAL system is operating. Occasionally, there may be a slight brake pedal pulsation when the RWAL system makes a pressure correction.
The RWAL system conducts a system self-check when the ignition switch is turned on. The "Rr ABS" lamp will stay on for about two seconds after the engine starts, then goes out when the system finds no faults.
here is no scheduled routine maintenance for the RWAL system beyond the required normal brake system maintenance items. If any problem occurs in the normal brake system that causes the "BRAKE" indicator lamp to light, the RWAL system will disable itself and the "Rr ABS" indicator lamp will also come on.
The RWAL system will operate while the vehicle is in 4-wheel drive (transfer case in 4L or 4H); however, if the front brakes lock in 4WD, the rear wheels will also lock, regardless of RWAL system operation, because they are mechanically connected to the front wheels through the transfer case.
The RWAL system includes:
^ Speed sensor
^ Electronic Brake Control Module (EBCM)
^ Anti-lock hydraulic valve assembly
^ Brake pedal switch (stoplight switch)
^ Front axle switch (4WD models)
^ Brake pressure differential switch
^ "Rr ABS" and "BRAKE" indicator lamps