C054DVacuum Sensor B Circuit/Open
- Generic OBD-II code · Chassis
- Can trigger limp mode
- How the car detects it
- Circuit fault on a second vacuum sensor, labelled B, typically an open in its signal, ground or feed. Some systems carry more than one vacuum measurement, for example a booster sensor next to one on the pump or supply line, but which sensor is B is not published by any maker, and no manufacturer documents C054D. The monitoring follows the same pattern as for sensor A: Mitsubishi's brake unit in the 2023 Outlander PHEV recognises an open, a short or a noisy vacuum sensor signal within a second (its own code C1073) and drops brake assist. HELLA's sensor wiring is simple – one pin each for output, ground and supply – so inspection starts at the connector. C0549 is the same fault on sensor A; C054E to C0550 are plausibility, low and high faults of B.
- What you may notice
- Brake system or brake assist warning
- Vacuum pump control in fallback, pump running longer
- Likely causes
- LikelyConnector of sensor B unplugged, loose or corroded
- PossibleInterrupted wire in the sensor harness
- RareSensor B open internally
- 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.