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OPERATION Accumulators in the valve body store extra fluid released to the system for ABS mode operation. The pump provides The valves modulate brake pressure during antilock braking and are controlled by the ABM. The HCU provides three channel ABS or four channel With Traction Control pressure control to the front and rear During antilock braking, the solenoid valves are opened and closed as needed. During normal braking, the HCU solenoid valves and pump are not activated. The master cylinder and power NOTE: The three modes mentioned below do occur but not necessarily in the order listed everytime. During antilock braking, solenoid valve pressure modulation occurs in three stages, pressure increase, pressure PRESSURE DECREASE The outlet valve is opened and the inlet valve is closed during the pressure decrease cycle. A pressure decrease cycle is initiated when speed sensor signals indicate high wheel slip at one or more wheels. At Once the period of high wheel slip has ended, the ABM closes the outlet valve and begins a pressure increase or PRESSURE HOLD Both solenoid valves are closed in the pressure hold cycle but only the inlet valve is energized. Fluid apply pressure PRESSURE INCREASE The inlet valve is open and the outlet valve is closed during the pressure increase cycle. The pressure increase REMOVAL 1. Disconnect the battery cables from the battery. 5 - 242 BRAKES - ABS SERVICE INFORMATION ND |