ABS 5.3 (3-channel system) system description · ABS operation This function and the input sig

ABS 5.3 (3-channel system) system description ABS operation This function and the input signals are continu- The ABS control module receives a signal from ously monitored. If a fault is detected, the COrl,- the brake~ightswitch and the AC voltage signals trol unit switchesthe ABS function off I switches on the ABS warning light and stores the fault infrom the four speed sensors. These signals are a non-volatilememory in the control unit.converted into digital wheel-speedsignals inde- pendentlyof each other by two microproces- In addition, whenevera journey is begun and asors. The wheel slip (approximatelyproportional speed of 6 km/h is exceeded,a testto the computed vehicle reference speed) is for- programme is started. The solenoid valves andmed from these wheel-speedsignals. the pump motor are electrically actuated and checked. If a fault is detected, the controlIf vehicle deceleration and excess slip at a module switchesthe ABS function off, the ABSwheel are detected..the pressure-holdingphase warning light is switched on and the fault isis initiated, i.e. the inlet valve for the relevant stored.wheel is closed to prevent a further increase in pressure. If in spite of the pressure being held constant the wheel tends to continue to lock up, the pressure in the wheel cylinder is reduced. For this purpose, the outlet valve is opened and the brake fluid is pumped back to the brake master cylinder via the return pump (pressure-re- duction phase)until the wheel turns again. Then, depending on the control cycle, further appro- priate cycles are initiated. 0 -26 0 Running gear -general 996O_16 Printed in Germany, 1997