P0551
Power Steering Pressure Sensor Circuit Malfunction
Powertrain Chassis/Safety Power Steering System 🟡 Moderate — Fix within a week
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What This Actually Means
In plain language — no jargon

Your car's power steering pressure sensor is sending a bad signal to the engine computer, like a broken gauge at a gas station. The steering system may not work correctly because the computer can't read the pressure properly.

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Symptoms You May Notice
3 known symptoms for this code
Stiff or heavy steering wheel
Power steering warning light on dashboard
Steering assist cuts in and out intermittently
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Embedded Systems Insight
What the ECU/ECM is actually computing

The ECU monitors voltage output from the power steering pressure sensor to verify hydraulic system pressure is within safe operating range. It detects open circuits, short circuits, or out-of-range voltage signals that indicate sensor failure or wiring issues.

Voltage & Parameter Thresholds

Parameter Normal Range Fault Condition
Sensor Voltage Output 0.5–4.5 volts proportional to pressure Below 0.1V or above 4.9V, or fixed voltage
Pressure Reading 50–200 PSI at idle to load conditions Implausibly high or impossibly low reading
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Diagnostic & DIY Fix Guide
Check these in order — from cheapest to most complex
1
Power steering pressure sensor connector
Inspect and reseat the connector at the sensor; corrosion or loose pins often trigger this code.
2
Power steering pressure sensor wiring
Check wiring harness for cuts, pinches, or corrosion between sensor and ECU; repair or replace damaged sections.
3
Power steering pressure sensor
Replace the sensor if connector and wiring are intact; sensor internal failure is the most common cause.