Normal Operation And Fault Conditions

WARNING: This page does not describe the selected car, but rather 9 other vehicles, including the 2021 Lincoln Corsair, 2021 Ford Transit-350 HD, 2021 Ford Transit-350, 2021 Ford Transit-250, and 2021 Ford Transit-150. However, it is still accessible from the selected car via links, so may be relevant.

With the ignition OFF and the engine not running, the HydroMax pump motor is controlled by brake pedal application through the use of the brake signal isolation relay and the HydroMax pump motor relay. When the engine is not running the HydroMax flow switch is closed and the HydroMax pump motor relay is grounded through the flow switch. When the driver presses the brake pedal, voltage is sent to the brake signal isolation relay, which then sends voltage to the HydroMax pump motor relay causing the pump motor to activate.

With the ignition ON and the engine not running, the HydroMax pump motor is controlled by the ABS module through the use of the HydroMax pump motor relay. When the engine is not running the HydroMax flow switch is closed and the HydroMax pump motor relay is grounded through the flow switch. When the ignition is turned to ON and the brake pedal is pressed, the ABS module activates the HydroMax pump motor relay, which then sends voltage to the HydroMax pump motor relay causing the pump motor to activate.

With the ignition ON and the engine running, the HydroMax pump motor is controlled by the ABS module and brake pedal application through the use of the brake signal isolation relay and the HydroMax pump motor relay. When the engine is running the HydroMax flow switch is open and the HydroMax pump motor relay is grounded through the ABS module. The driver presses the brake pedal which sends voltage to the brake signal isolation relay, which then sends voltage to the HydroMax pump motor relay causing the pump motor to activate.

The ABS module monitors the pump motor activation through a hardwired connection at the pump motor voltage supply circuit. When the pump motor relay activates, voltage is sent to the pump motor and the ABS module measures the voltage drop across the pump motor. A shorted or open pump motor, a shorted or open circuit, a inoperative or stuck relay, or a loose electrical connector results in the ABS module setting one or more DTCs.

The brake signal isolation relay provides the voltage necessary for HydroMax pump motor relay operation. This voltage is sent to the HydroMax pump motor relay and the ABS module. The ABS module continually monitors the brake signal isolation relay switch output and sets a DTC if the relay is stuck closed, there is an open fuse or a circuit failure on the brake signal isolation relay switch output circuit.

PPT CS ABS MODULE DTC FAULT TRIGGER CONDITIONS

DTC	Description	Fault Trigger Conditions
C1052:77	Hydraulic Brake Booster Motor: Commanded Position Not Reachable	This DTC sets when if the HydroMax pump motor activates without a braking request from the driver or input from the ABS module. This is most likely due to a relay or circuit failure. The DTC can only be cleared by driving the vehicle above 24 km/h (15 mph) once the cause of the DTC has been repaired.
C1052:79	Hydraulic Brake Booster Motor: Mechanical Linkage Failure	With the ignition ON, the engine not running and system voltage between 9 and 16 volts, this DTC sets when the ABS module Hydromax flow switch circuit monitoring has determined the Hydromax flow switch is closed when the Hydromax motor is running for more than 1 second. The DTC can only be cleared by driving the vehicle above 24 km/h (15 mph) once the cause of the DTC has been repaired.
C1052:7E	Hydraulic Brake Booster Motor: Actuator Stuck On	When the ignition is set to ON, the ABS module carries out a system check. If the Hydromax motor remains running for more than 1 second, this DTC sets.
C1052:7F	Hydraulic Brake Booster Motor: Actuator Stuck Off	There are 3 different setting criteria for this DTC; 1) if the HydroMax flow switch remains closed for more than 1 second while the PCM CAN message indicates the engine is not running, 2) the HydroMax flow switch remains open for more than 1 second while the PCM CAN message indicate the engine is running or 3) when both the high side and low side inputs are enabled but the HydroMax pump motor is not running.
C1053:13	Hydraulic Brake Booster High Side Driver: Circuit Open	With the ignition ON and system voltage between 9 and 16 volts, this DTC sets when the ABS module detects voltage outside a range of 0.5-6.8 volts on the HydroMax relay power circuit.
C1055:7E	Hydraulic Brake Booster M Line: Actuator Stuck On	With the ignition ON and system voltage between 9 and 16 volts, this DTC sets when a circuit failure is detected on the HydroMax flow switch motor for more than 5 seconds.
C1056:64	Hydraulic Brake Booster Brake Light Switch Isolation Relay: Signal Plausibility Failure	With the ignition ON, system voltage between 9 and 16 volts, the engine is running and the brake pedal is applied (HydroMax flow switch is open), if the ABS module detects the voltage at the HydroMax flow switch to be less than 55% of system voltage, this DTC is set.
C1057:14	Hydraulic Brake Booster General Relay: Circuit Short To Ground or Open	With the ignition ON, system voltage between 9 and 16 volts, and the engine is not running, if the ABS module detects the HydroMax pump motor is not running when the brake pedal is applied for more than 1 second, this DTC is set.
C1057:15	Hydraulic Brake Booster General Relay: Circuit Short To Battery or Open	With the ignition ON, system voltage between 9 and 16 volts, and the engine is running, if the ABS module detects the HydroMax pump motor is running for more than 1 second, this DTC is set.