What it means
Vacuum sensor B signal voltage below expected range. Wiring faults of this kind typically come from chafing, water ingress at connector seals, or pin push-back — a wiggle test on the harness while the code is active often confirms the location.
How it works
Vacuum sensor B provides a signal the control module uses to assess vacuum available for brake assist. C054F sets when the voltage on sensor B's signal circuit falls below the module's expected range, which can result from a short to ground or a poor connection.
Common causes
Most likely first.
- Signal wire shorted to ground
- Connector pins corroded - high contact resistance
- Harness chafing through insulation
Symptoms
- Brake or stability-control warning light on
- Brake assist may be affected
How to diagnose it
- Record freeze-frame data and check live data for vacuum sensor B to confirm whether its signal remains low while the code is active.
- Inspect sensor B's harness for chafing or crushed insulation, especially where it passes near brackets or moving parts.
- Check sensor B's connector for water ingress, corrosion, loose terminals, or a pin pushed back into the connector body.
- With the wiring diagram, test the signal wire for a short to ground and check connector contact quality while gently moving the harness.
- If the wiring and terminals pass, check sensor B's supply, ground, and output against the manufacturer's specification.
Common fixes
- Repair chafed insulation or a signal wire shorted to ground.
- Clean and dry sensor B's connector, replace damaged terminals, and restore its seal.
- Repair a loose or pushed-back connector pin to restore contact.
- Replace vacuum sensor B if its signal remains low despite a sound circuit and correct supply.
Can I keep driving?
Drive cautiously and leave extra stopping distance because brake assist may be affected. If the pedal becomes hard or the vehicle does not brake normally, stop safely and arrange assistance.
A code shows where the control module detected a fault, not always which part failed. Check the causes in order and confirm with a test before replacing parts. Have several codes? Check them together
This is a generic code: it means the same on every make. The car’s maker may add more detail in its own service information.