P055B - Power Steering Pressure Sensor B Circuit Range/Performance
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System
Powertrain (Engine & Gearbox)
Related Fault Codes
Technical Description
Diagnostic Trouble Code (DTC) P055B is set when the Engine Control Module (ECM) detects that the Power Steering Pressure (PSP) sensor 'B' signal is outside of the expected range or is not performing correctly relative to engine load and steering input. The sensor monitors hydraulic pressure to allow the ECM to adjust idle speed (IAC) and engine torque to compensate for the additional load from the power steering pump. P055B specifically identifies a range/performance issue, meaning the signal is within electrical limits but does not make sense logically based on operating conditions.
Possible Causes
Faulty Power Steering Pressure (PSP) sensor (internal leak or diaphragm failure)
Low power steering fluid level or air in the hydraulic system
Damaged wiring or corrosion in the connector (high resistance)
Worn power steering pump not generating sufficient pressure
Symptoms
Recommended Solution
- Visual Inspection: Check power steering fluid level and look for leaks around the sensor. Inspect the connector for oil contamination.
- Measurement: Use a multimeter to verify 5.0V reference voltage and ground at the sensor. With Key On/Engine Off, the signal voltage should typically be around 0.5V.
- Advanced Diagnosis: Use a scan tool to monitor 'Power Steering Pressure' PID in real-time. Pressure should be low at rest and increase significantly during steering input (reaching 1000+ PSI / 70+ Bar at full lock). If the value is static or erratic, the sensor is faulty.
- Action: Replace the sensor if the wiring is intact but signal values are irrational.
Mechanic's Tip
Before replacing expensive components, always double-check wiring and connections. 80% of all sensor faults are actually due to corroded contacts or broken wires.
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