What Does P0551 Mean?
The ECM has detected that the power steering pressure sensor signal is not responding as expected for the current operating conditions. The sensor output does not change appropriately when steering effort changes, or the signal is outside the expected range/performance window. This range/performance code indicates the sensor may be reading but is inaccurate or sluggish rather than completely failed.
Common Causes
35%
Degraded power steering pressure sensor with drift in calibration or sluggish response to pressure changes
25%
Low or contaminated power steering fluid causing abnormal system pressures that fall outside the sensor's expected range
25%
Intermittent connection at the PSP sensor connector causing signal dropouts during steering maneuvers
15%
Failing power steering pump unable to generate proper pressure, causing the sensor to read outside expected parameters
Diagnostic Steps
1
Step 1: Check the power steering fluid level and condition. Low, foamy, or contaminated fluid can cause erratic pressure readings. Top off or flush the system if the fluid is dark, burned-smelling, or has air bubbles.
2
Step 2: Install a mechanical power steering pressure gauge in series with the high-pressure line. Compare the mechanical gauge reading to the ECM's reported PSP sensor value at idle and full lock. Deviation of more than 100 psi indicates a sensor calibration issue.
3
Step 3: Monitor the PSP sensor live data while performing slow lock-to-lock steering. The signal should transition smoothly without sudden drops or plateaus. Erratic signal indicates a sensor or connection fault.
4
Step 4: Wiggle-test the PSP sensor connector and harness while monitoring the live data stream. Any signal dropout during manipulation confirms an intermittent connection.
5
Step 5: If the power steering pump pressure is low on the mechanical gauge (below 800-1000 psi at full lock), the pump may be the root cause. Replace the PSP sensor if it does not match the mechanical gauge reading and the system pressure is confirmed normal.
Estimated Repair Cost
$50 - $250
Parts + labor, varies by vehicle and location
The ECM has detected that the power steering pressure sensor signal is not responding as expected for the current operating conditions. The sensor output does not change appropriately when steering effort changes, or the signal is outside the expected range/performance window. This range/performance...
The most common cause of P0551 (Power Steering Pressure Sensor Circuit Range/Performance) is: Degraded power steering pressure sensor with drift in calibration or sluggish response to pressure changes
Typical repair costs for P0551 range from $50 to $250, depending on the vehicle, location, and whether you do it yourself or go to a shop.
Inaccurate PSP sensor readings prevent proper idle speed compensation during steering, potentially causing idle sag or stalling during low-speed maneuvers such as parking.
Start by connecting an OBD2 scanner to read the code and any freeze frame data. Then follow the diagnostic steps specific to P0551 to identify the root cause.
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Quick Info
Category
Powertrain
System
Power Steering / Engine Idle Control System
Difficulty
Type
Generic (SAE)
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