What does it mean?
C1248 is a Chassis (ABS, traction control, steering) fault code. It indicates: Brake Booster Pump Motor Circuit Failure . This is a standardised OBD-II code. The technical definition is the same regardless of the make or model of vehicle, although specific causes and symptoms can vary between vehicles.
Symptoms
- Hard, high brake pedal that needs much more effort than normal
- Brake and ABS warning lamps on, often with an audible warning
- Pump not running at all, or running for long periods and sounding strained
- Noticeably longer stopping distances, which makes the vehicle unsafe to drive
- Warning message about the brake system on vehicles with a driver display
- Battery drain if the pump runs continuously
Likely causes
- Blown pump fuse or fusible link in the high current supply
- Failed pump relay or its control circuit from the module
- Worn motor brushes, an open winding or a seized pump motor
- Corroded or loose power and ground connections at the pump
- Low brake fluid level or a restricted reservoir feed, making the pump run long and overheat
- Internal leak in the accumulator or hydraulic unit, so the pump runs constantly and eventually fails
- Damaged pump wiring where it flexes near the mounting
How to fix it
- Treat the vehicle as unsafe until the boost function is restored and follow the depressurisation procedure before opening the system
- Check the brake fluid level and top up correctly, then look for external leaks
- Listen for the pump at key-on and check the dedicated high current fuse and relay
- Measure supply voltage and ground at the pump under load, and voltage drop test both sides
- Read accumulator or system pressure on the scan tool and see whether pressure holds after the pump stops
- Check whether the pump runs constantly, which points to an internal leak or a failed accumulator rather than the motor
- Replace the pump or booster assembly as specified, then bleed and re-initialise the system