P0558
Brake Booster Pressure Sensor Circuit High Input
Powertrain Chassis/Safety Brake System Diagnostics 🟡 Moderate — Fix within a week
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What This Actually Means
In plain language — no jargon

The brake booster pressure sensor is reading a voltage that's too high, like a gauge needle stuck too far to the right. This tells the engine computer the brake system has more pressure than it should, which doesn't match reality.

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Symptoms You May Notice
3 known symptoms for this code
Brake warning light illuminated on dashboard
Hard or stiff brake pedal requiring excessive pressure
Reduced braking effectiveness or longer stopping distances
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Embedded Systems Insight
What the ECU/ECM is actually computing

The ECU monitors the brake booster pressure sensor voltage to ensure adequate vacuum pressure assists braking. When voltage exceeds the maximum threshold (typically 4.5V+), the ECU interprets this as abnormally high pressure and triggers the fault code. The sensor uses a variable resistor design where higher pressure produces higher voltage output.

Voltage & Parameter Thresholds

Parameter Normal Range Fault Condition
Sensor Voltage 0.5 - 4.5V (proportional to booster vacuum) >4.5V (circuit high condition)
Booster Pressure 15-21 inHg vacuum Below 15 inHg or sensor signal voltage excessive
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Diagnostic & DIY Fix Guide
Check these in order — from cheapest to most complex
1
Sensor wiring harness
Inspect connector for corrosion, loose pins, or water intrusion and clean with electrical contact cleaner.
2
Brake booster vacuum hose
Check for cracks, splits, or disconnection from intake manifold and replace if damaged.
3
Brake booster pressure sensor
Replace the sensor unit if wiring and hoses are intact, as internal circuit failure causes high voltage output.