What Does P0550 Mean?
The ECM has detected a general malfunction in the power steering pressure (PSP) sensor circuit. The PSP sensor provides the ECM with hydraulic pressure information so it can compensate idle speed when the steering wheel is turned against the stops or during low-speed maneuvering. A circuit malfunction means the sensor signal is missing, erratic, or outside the valid voltage range.
Common Causes
35%
Failed power steering pressure sensor with internal circuit failure producing no signal or erratic output
30%
Damaged or corroded wiring and connector at the PSP sensor, often from power steering fluid leaks
20%
Open or short circuit in the wiring between the PSP sensor and ECM due to chafing or rodent damage
15%
ECM internal fault on the PSP sensor input circuit or reference voltage supply
Diagnostic Steps
1
Step 1: Locate the power steering pressure sensor (typically threaded into the high-pressure line or power steering pump). Inspect for fluid leaks around the sensor and check the connector for oil contamination, corrosion, or damage.
2
Step 2: With the key on engine off, backprobe the PSP sensor connector to verify 5V reference voltage and ground are present. The signal wire should read approximately 0.5V with no steering input.
3
Step 3: Start the engine and turn the steering wheel to full lock while monitoring the PSP sensor voltage. The signal should rise smoothly from approximately 0.5V to 4.0-4.5V as pressure increases. Erratic or fixed readings indicate a sensor fault.
4
Step 4: If reference voltage or ground is missing at the sensor connector, trace the wiring back to the ECM. Check for open circuits, shorts, and chafed wires along the harness route.
5
Step 5: If wiring is intact but the sensor produces no valid signal, replace the power steering pressure sensor. Use a new O-ring and torque to specification (typically 15-20 ft-lbs). Clear codes and verify proper operation.
Estimated Repair Cost
$50 - $200
Parts + labor, varies by vehicle and location
The ECM has detected a general malfunction in the power steering pressure (PSP) sensor circuit. The PSP sensor provides the ECM with hydraulic pressure information so it can compensate idle speed when the steering wheel is turned against the stops or during low-speed maneuvering. A circuit malfuncti...
The most common cause of P0550 (Power Steering Pressure Sensor Circuit Malfunction) is: Failed power steering pressure sensor with internal circuit failure producing no signal or erratic output
Typical repair costs for P0550 range from $50 to $200, depending on the vehicle, location, and whether you do it yourself or go to a shop.
The primary symptom is engine idle drop or stalling when the steering wheel is turned at low speeds or at parking stops. While not directly dangerous, unexpected stalling during parking maneuvers could momentarily affect vehicle control.
Start by connecting an OBD2 scanner to read the code and any freeze frame data. Then follow the diagnostic steps specific to P0550 to identify the root cause.
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Quick Info
Category
Powertrain
System
Power Steering / Engine Idle Control System
Difficulty
Type
Generic (SAE)
Recommended Tools
OBD2 Scanner
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