P0558 moderate

Brake Booster Pressure Sensor Circuit High

The P0558 code means the vehicle's onboard diagnostic system has detected: Brake Booster Pressure Sensor Circuit High. 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
False high pressure reading
Start/stop system disabled
No idle speed compensation for brake booster

Probable Causes (Ranked by Likelihood)

Open circuit in brake booster sensor wiring Very High
Failed sensor reading high (open internally) High
Disconnected sensor connector Moderate
Corroded pins causing high resistance Moderate

Step-by-Step Diagnostic Procedure

Read sensor value; an abnormally high voltage regardless of engine vacuum confirms circuit high
Check sensor connector for disconnection or corrosion
Measure sensor output voltage; a reading stuck near reference voltage indicates an open circuit
Test sensor with a hand vacuum pump to verify it responds to vacuum changes

Frequently Asked Questions

What does circuit high mean for P0558?

Circuit high means the sensor signal voltage is above the expected maximum. This usually indicates an open circuit in the sensor or wiring, causing the reference voltage to read through. The ECM sees this as no vacuum in the brake booster.

Is P0558 a brake safety concern?

P0558 does not directly affect brake booster operation. The brakes still work normally with vacuum assist. However, the ECM cannot monitor booster vacuum level, which may be important for safety features like the start/stop system.

Can a disconnected wire cause P0558?

Yes. A disconnected sensor connector is one of the most common causes of P0558. Check the sensor connector first before replacing the sensor itself. The connector may have vibrated loose or corroded.