Chart C-1 Pump Motor Circuits

PRESSURE MONITORING MODULE

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, antilock 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 14,500 kPa (2100 psi) and to turn the pump motor off at approximately 18,000 kPa (2600 psi).

PUMP CIRCUIT OPERATION

The pump relay coil is provided power at key-on through the over-voltage 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 the 56-way engine connector which is located under the right side dash near the ECM. 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 31. This circuit is not used by the EBCM and is included in the harness to facilitate testing.