Chassis, generic

C054E Vacuum Sensor B Range/Performance

Check engine lightUsually off
EmissionsNot relevant
Drive cycleRequired
Limp modePossible

Sensor B reports a plausible-looking voltage, but the vacuum it represents contradicts the expected value. With two vacuum sensors a module can also compare them with each other; publicly, the comparison methods come from patents on booster sensors: Ford treats booster pressure lying clearly above manifold pressure as sensor degradation, since a working check valve prevents that state, and checks whether booster pressure moves after brake applications; GM tracks booster vacuum against MAP-based engine vacuum with the throttle closed. A real leak or a weak pump can look identical, so the vacuum system is tested before replacing the sensor. No maker documents C054E publicly, and the meaning of B is maker-specific. C054A is the counterpart on sensor A.

Likely causes

Sensor B drifting or fouled
Leak, faulty check valve or weak vacuum pump
Wrong sensor type fitted after repair

Symptoms

  • Brake assist or brake system warning
  • Pedal feels firmer after several brake applications

Repair estimate

DifficultyMediumDIY possible
Parts and labour€30–400
Time0.3–2 h

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

Parts involved

vacuum sensor b

Related codes

C054DC054FC0550C054AP0556

References: patents.google.com, patents.google.com, hella.com.