P0555 moderate

Brake Booster Pressure Sensor Circuit

The P0555 code means the vehicle's onboard diagnostic system has detected: Brake Booster Pressure Sensor Circuit. This is a moderate severity code.

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Keep driving?: Short distances only
DIY difficulty: moderate
Estimated cost: $100 - $400 (parts and labor)

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Common Symptoms

Check Engine Light on
Brake booster performance warning
Hard brake pedal in some conditions
Start/stop system disabled

Probable Causes (Ranked by Likelihood)

Faulty brake booster pressure sensor Very High
Wiring fault in brake booster sensor circuit High
Vacuum leak at brake booster hose Moderate
ECM input circuit failure Low

Step-by-Step Diagnostic Procedure

Read brake booster pressure sensor value with a scan tool; compare to expected vacuum reading
Inspect the brake booster vacuum hose for cracks, disconnection, or collapse
Check the sensor connector and wiring for damage or corrosion
Measure sensor output voltage at different vacuum levels if a hand vacuum pump is available

Frequently Asked Questions

What does the brake booster pressure sensor do?

The brake booster pressure sensor monitors the vacuum level in the brake booster. The ECM uses this data to ensure sufficient vacuum is available for power braking, to manage engine idle speed, and to control the start/stop system on equipped vehicles.

Can P0555 affect braking?

P0555 itself does not directly reduce braking power, but it indicates the ECM cannot monitor brake booster vacuum. The ECM may disable the start/stop system and may not properly adjust idle speed to maintain brake booster vacuum.

Is P0555 related to the start/stop system?

Yes. The start/stop system uses brake booster pressure data to ensure the brakes have sufficient vacuum assist before allowing the engine to shut off at a stop. If this data is unavailable, the system is disabled.