C0556
Brake Booster Pressure Sensor Performance
The brake booster vacuum or pressure sensor signal does not respond plausibly to engine vacuum or electric booster activity.
The brake booster vacuum or pressure sensor signal does not respond plausibly to engine vacuum or electric booster activity.
Common causes
- high
Vacuum leak in booster line
One of the most commonly reported causes for this code — check this first.
Typical part cost: $70-660
- medium
Vacuum pump weak
A plausible cause — test and verify before replacing parts.
Typical part cost: $70-660
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First things to check
- 1Confirm the code with a scan tool and check for additional related codes.
- 2Inspect the relevant sensors, wiring, and connectors for damage or corrosion.
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Related codes
See related trouble codes
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Frequently asked questions
What does C0556 mean?
C0556 means "Brake Booster Pressure Sensor Performance". It is a generic OBD-II code that points to a fault in the chassis.
What are the most common causes of C0556?
vacuum leak in booster line; vacuum pump weak; sensor element aged beyond calibration window — these are the most commonly reported causes. Verify with a proper diagnosis before replacing parts, or use the Wrenchify app for a vehicle-specific diagnosis.
Can I keep driving with this code?
The vehicle is usually drivable for short distances, but the problem can worsen or affect emissions. Diagnose and repair as soon as practical. Use the Wrenchify app for a full diagnosis specific to your vehicle.
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