What does it mean?
C1257 is a Chassis (ABS, traction control, steering) fault code. It indicates: Brake Booster Pump Motor Relay Control 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
- Pump motor never runs, or runs continuously even with the key off
- Hard brake pedal with reduced assist, or a battery that goes flat overnight if the relay stays energised
- Brake, ABS and stability lamps illuminated
- Code sets as soon as the ignition is switched on
- Traction and stability control unavailable
Likely causes
- Open circuit or high resistance in the control wire between the control module and the relay coil
- Relay coil open or shorted internally
- Short to battery voltage on the control circuit holding the relay energised
- Short to ground on the control circuit so the relay cannot be switched off
- Corroded or spread terminals in the relay socket
- Harness damage where the circuit passes the bulkhead or a moving bracket
- Failed driver inside the ABS/brake control module
How to fix it
- Command the relay on and off with the scan tool bi-directional function and listen for the click
- Measure the relay coil resistance and compare it with the specification
- Unplug the relay and check the control terminal for unexpected battery voltage, which indicates a short to power
- Check the control wire for continuity to the module pin and for a short to ground
- Inspect the relay socket and connector for corrosion, pushed-out pins and loose fits
- Repair the harness or replace the relay, then clear the codes and verify correct pump operation
- Replace the control module only after the coil and the wiring have tested good