C054BVacuum Sensor A Circuit Low
- Generic OBD-II code · Chassis
- Can trigger limp mode
- How the car detects it
- The signal of vacuum sensor A has fallen below the lowest voltage a working sensor can produce. In HELLA's design the output runs from 0.5 V at no vacuum to 4.5 V at −1000 hPa and is clamped to a 0.4–4.8 V band, so anything under that floor must be electrical: a grounded signal line, an absent 5-V feed or an internally failed sensor. Because low voltage in such a characteristic means little or no vacuum, the brake control unit cannot trust the value and may run the electric pump as a precaution or block functions that depend on it, which Bosch names as pump control, stop-start and ESP assistance. Mitsubishi detects short circuits on its brake vacuum sensor within a second. No maker documents C054B publicly. C054C is the high counterpart.
- What you may notice
- Brake assist or brake system warning lit
- Electric vacuum pump running continuously
- Likely causes
- LikelySignal wire shorted to ground
- Possible5-V supply to the sensor missing
- RareSensor failed with output stuck low
- 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.