Pump Motor Circuits

Operation of the pump/motor assembly is controlled by the Pressure Monitoring Module in the Sensor Block, through the pump motor relay. The Pressure Monitoring Module includes a pressure switch with two redundant sensors which read accumulator pressure. Output from these two switches is compared to determine if the pressure switch assembly is operating properly. If the readings do not match, anti-lock function is disabled and the BRAKE warning lamp is illuminated.

The Pressure Monitoring Module is calibrated to turn the pump motor on at an accumulator pressure of approximately 2100 psi (14,500 kPa) and to turn the pump motor off at approximately 2600 psi (18,000 kPa).

PUMP CIRCUIT OPERATION

The pump relay coil is provided power at key-on through the overvoltage protection relay. The coil ground line (circuit 874) is held at 12 volts at all times with the ignition on. When pump operation is desired, the Pressure Monitoring Module grounds the relay coil at Sensor Block pin 6.

Power is supplied to the pump motor through a fusible link at the front chassis positive junction block. The power circuit from the relay to the pump (circuit 854) passes through a 2-way connector which is located near the center of the engine compartment next to the cowl. The pump motor is grounded on the engine block near the starter motor.

A pump motor monitoring line (circuit 854C) runs from the pump motor relay to EBCM connector pin 14. This circuit is not used by the EBCM and is included in the harness to facilitate testing.