Safety Warning
DIY auto repair can cause serious injury, fire, or vehicle damage. These guides are for informational purposes only. Always follow OEM torque specs, wear PPE, and consult a certified mechanic if you are unsure. You are solely responsible for your safety.
Normal Operation and Fault Conditions
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.
| 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 | This DTC sets when the ABS module detects a circuit error in the HydroMax pump motor circuit. |
| C1052:7E | Hydraulic Brake Booster Motor: Actuator Stuck On | This DTC sets when the ABS module detects the HydroMax pump motor is always running. This is most likely due to a relay, switch 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. |
| C1052:7F | Hydraulic Brake Booster Motor: Actuator Stuck Off | This DTC sets when the ABS module detects the HydroMax pump motor is never running when requested. This is most likely due to a relay, switch 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. |
| C1053:13 | Hydraulic Brake Booster High Side Driver: Circuit Open | This DTC sets when the ABS module detects a circuit error in the HydroMax relay control circuit. |
| C1055:7E | Hydraulic Brake Booster M Line: Actuator Stuck On | This DTC sets when the ABS module detects a circuit error in the HydroMax pump motor monitoring circuit. |
| C1056:64 | Hydraulic Brake Booster Brake Light Switch Isolation Relay: Signal Plausibility Failure | This DTC sets when the ABS module detects an open or a short to ground on the brake light isolation relay output circuit. |
| C1057:14 | Hydraulic Brake Booster General Relay: Circuit Short To Ground or Open | This DTC sets when the ABS module detects a short to ground on the high side of the HydroMax pump motor relay. |
| C1057:15 | Hydraulic Brake Booster General Relay: Circuit Short To Battery or Open | This DTC sets when the ABS module detects a short to battery voltage on the high side of the HydroMax pump motor relay. |
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When to See a Mechanic
Stop DIY work and contact a certified mechanic immediately if any of the following apply:
- • You smell fuel, burning insulation, or see smoke.
- • Brakes feel soft, pull hard to one side, or make grinding noises.
- • The engine overheats, stalls repeatedly, or misfires under load.
- • You are missing required tools, torque specs, or safe lifting equipment.
- • You are not confident in the next step or safety outcome.