What does it mean?
C1288 is a Chassis (ABS, traction control, steering) fault code. It indicates: Booster Position Sensor Circuit Malfunction .
Symptoms
- Brake pedal feel inconsistent, sometimes hard and sometimes over-assisted
- Red brake warning lamp with ABS and stability lamps
- Booster does not build assist in step with pedal travel
- Pedal or booster position value in live data does not follow the pedal smoothly
- Stability control and adaptive braking functions disabled
Likely causes
- Worn resistive track or internal failure inside the booster position sensor
- Open, short or high resistance in the sensor supply, ground or signal wiring
- Corroded or water-damaged connector at the booster assembly
- Sensor or pushrod out of adjustment so the reported travel does not match the pedal
- Loss of the 5 V reference shared with other sensors
- Sensor never calibrated after the booster or the module was replaced
- Brake control module input fault
How to fix it
- Watch the booster position value in live data while pressing the pedal slowly through its full travel and look for dropouts or dead spots
- Check the sensor connector for moisture, corrosion and loose terminals
- Measure the 5 V reference and the ground at the sensor with the ignition on
- Confirm the sensor mounting and the pushrod adjustment are correct
- Disconnect the sensor and test the circuits for open, short to ground and short to voltage
- Run the sensor calibration procedure where the vehicle supports it
- Replace the sensor or the booster assembly once the wiring and supplies are proven good