C0550Vacuum Sensor B Circuit High
- Generic OBD-II code · Chassis
- Can trigger limp mode
- How the car detects it
- Vacuum sensor B puts out more voltage than its design permits. HELLA caps the output of its booster sensor at 4.8 V, with 4.5 V already standing for −1000 hPa, so anything above is a wiring or sensor fault: signal touching the supply or battery voltage, a broken ground return or a failed sensor. Because a high voltage simulates strong vacuum, the control unit must not rely on it for switching the electric vacuum pump; Bosch describes that pump control as the core job of the measurement. Mitsubishi's brake unit catches vacuum sensor shorts within a second and suspends brake assist. No maker documents C0550 with this meaning; one GM bulletin cites C0550 at a rear differential clutch module, a GM-specific use. C054F is the low counterpart, C054C the same fault on A.
- What you may notice
- Brake assist or brake system warning on
- Firm pedal possible if the pump is not switched on when needed
- Likely causes
- LikelySignal of sensor B shorted to supply or battery voltage
- PossibleGround return of sensor B broken
- RareSensor B stuck at high output
- 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.