Chassis, generic

C054D Vacuum Sensor B Circuit/Open

Check engine lightUsually off
EmissionsNot relevant
Drive cycleNot required
Limp modePossible

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.

Likely causes

Connector of sensor B unplugged, loose or corroded
Interrupted wire in the sensor harness
Sensor B open internally

Symptoms

  • Brake system or brake assist warning
  • Vacuum pump control in fallback, pump running longer

Repair estimate

DifficultyEasyDIY possible
Parts and labour€20–250
Time0.2–1.5 h

Typical range across vehicles; the real cost depends on what the testing finds.

Parts involved

vacuum sensor bsensor wiring

Related codes

C054EC054FC0550C0549C0547

References: mitsubishitechinfo.com, hella.com, bosch-mobility.com.