What does it mean?
C1289 is a Chassis (ABS, traction control, steering) fault code. It indicates: Booster Pressure Sensor Circuit Malfunction . 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 pedal or assist that varies from stop to stop
- Red brake warning lamp together with ABS and stability lamps
- Pump cycling far more often than normal, or running continuously
- Pressure value in live data not near zero with the pedal released, or not rising when the pedal is pressed
- Longer stopping distances and stability control disabled
Likely causes
- Internal failure or drift of the booster pressure sensor
- Open, short or high resistance in the sensor supply, ground or signal circuit
- Corroded or moisture-filled connector at the sensor
- Loss of the 5 V reference feeding the sensor
- Genuine hydraulic problem such as low fluid, air in the system or a failed accumulator giving an out-of-range pressure
- Sensor not calibrated after replacement of the booster or module
- Brake control module input fault
How to fix it
- Check the brake fluid level and inspect the system for leaks before electrical testing
- Read the pressure value with the pedal released and then pressed, and compare the change with what is expected
- Measure the sensor supply and ground at the connector with the ignition on
- Disconnect the sensor and test each circuit for open, short to ground and short to voltage
- Bleed the system if air is suspected, and check the accumulator condition where the design uses one
- Run any required sensor calibration after a repair
- Replace the pressure sensor or the booster assembly once the wiring and hydraulics test good