Normal Operation and Fault Conditions

The hydraulic flow switch detects the fluid flow from the power steering system. When the engine is running, the power steering fluid is flowing and the switch is open. When the engine is off, the power steering fluid is not flowing and the switch is closed.

With the engine running, the flow switch is open and the hydraulic pump motor relay coil is grounded through the ABS module. Because the engine is running and brake boost is provided by the power steering system, the ABS module only activates the pump motor when extra stopping power is needed or there is a failure in the power steering system.

When the engine is not running, the flow switch is closed and the hydraulic pump motor relay coil has a direct connection to ground. When the brake pedal is pressed, the pump motor activates.

PPT CR ABS MODULE DTC FAULT TRIGGER CONDITIONS

DTC	Description	Fault Trigger Conditions
C1050:9E	Hydraulic Brake Booster Flow Switch: Stuck Off	With the ignition ON, the engine running, system voltage between 9 and 16 volts, and there no PCM communication DTCs present, this DTC sets when the ABS module detects the HydroMax pump motor is running for 2 seconds while the ABS module is receiving the BOO CAN message from the PCM indicating the brake pedal is applied.
C1050:9F	Hydraulic Brake Booster Flow Switch: Stuck On	With the ignition ON, the engine not running and system voltage between 9 and 16 volts, this DTC sets when the HydroMax pump motor continues to run for more than 1 second.
C1057:13	Hydraulic Brake Booster General Relay: Circuit Open	With the ignition ON, the engine not running, system voltage between 9 and 16 volts, and no PCM communication DTCs present, this DTC sets when the ABS module detects the pump motor running for more than 1 second while the PCM CAN message indicates the brake pedal is not applied.