C054CVacuum Sensor A Circuit High
- Generic OBD-II code · Chassis
- Can trigger limp mode
- How the car detects it
- Vacuum sensor A reports a voltage above its upper clamp. HELLA's booster sensor never exceeds 4.8 V when intact, even at full vacuum, so a higher reading indicates a signal shorted to the 5-V supply or to battery voltage, an open ground, or an internal defect. On a characteristic where more volts mean more vacuum, such a fault pretends a deep vacuum that may not exist; that is the riskier direction, because the electric pump could stay off. Brake units therefore check the circuit continuously; the 2023 Mitsubishi Outlander PHEV reports a shorted vacuum sensor circuit in at most one second and suspends brake assist. Bosch describes the sensor as the input for pump control and stop-start. No maker documents C054C publicly. C054B is the low counterpart, C0550 the same fault on sensor B.
- What you may notice
- Brake assist warning on
- Harder brake pedal if the booster really runs short of vacuum
- Likely causes
- LikelySignal line shorted to supply or battery voltage
- PossibleSensor ground interrupted
- RareSensor failed with output stuck high
- Repair
- Easy · Often possible to do yourself.Typical cost: €20 – €250
- Related codes
Explanation from obdex (CC0), exactly as the app shows it. Guidance only; confirm with a workshop.