Code
P1550
SCION
P — Powertrain
Power steering pressure sensor circuit malfunction
Views:
UK: 0
EN: 4
RU: 4
AI status
Completed
Completed
100%
Causes
- Damaged or corroded sensor connector or wiring (open, short to ground or to power)
- Faulty power steering pressure sensor (internal short or failed element)
- Poor electrical ground at sensor or ECM
- Faulty ECU/PCM input circuit (less common)
- Contamination, oil intrusion, or mechanical damage to the sensor
Symptoms
- Malfunction Indicator Lamp (MIL) illuminated (Check Engine light)
- Reduced or inconsistent power steering assist or increased steering effort (if vehicle uses hydraulic assist)
- Erratic idle or stalling in some vehicles that use steering pressure input for idle control
- Stored DTC and possible limp/limited assist state on some systems
What to check
- Retrieve freeze-frame and live data with a scan tool; note conditions when code set (engine load, rpm, steering input)
- Visual inspection of sensor, connector, and wiring for damage, oil contamination, corrosion, or loose pins
- Check for any related stored codes (power supply, ground, communication)
- Back-probe the sensor connector with key ON (engine OFF) to check reference voltage, signal voltage, and ground
- Wiggle test wiring while monitoring live signal to reproduce fault
- Inspect related fuses and ground points
Signal parameters
- Typical reference voltage: ~5.0 V (verify factory spec for vehicle)
- Typical signal output: about 0.5–4.5 V depending on pressure (varies by sensor)
- Expected change in signal when steering wheel is turned or pump loaded: signal should vary smoothly without dropouts
- Resistance between sensor signal and ground: consult service manual for exact ohms — look for open or short to ground/power
Diagnostic algorithm
- Read DTC(s) and freeze frame with a scan tool; note conditions when fault occurred.
- Perform a careful visual inspection of the power steering pressure sensor, harness, and connector. Remove corrosion, dry oil contamination, and reseat connector.
- Back-probe the sensor harness: with ignition ON (engine OFF) verify reference voltage (usually ~5 V), ground continuity, and steady signal voltage. Record values.
- Start engine and observe live signal while turning steering lock-to-lock or with steering input to see signal variation. Look for intermittent drops or stuck values.
- If reference or ground is missing, trace wiring to the fuse/ECM and repair open/short. If signal is shorted to 12 V or ground, isolate and repair wiring harness.
- Perform continuity and resistance checks between sensor connector and ECM connector to detect internal wiring faults or shorts to chassis.
- If wiring and connectors are good but signal still out of range, replace the power steering pressure sensor and retest.
- After repair clear codes and perform a test drive with scan tool to confirm the code does not return. If persistent and wiring verified, consider ECU input failure and consult manufacturer technical service information.
Likely causes
- Intermittent connector contact or bent terminal at sensor harness
- Chafed wiring contacting chassis or hot engine components
- Sensor failed after contamination with fluid or heat exposure
- Blown fuse or poor fused power supply to sensor circuit (if applicable)
Fault status
Status
Stored when the engine control module detects an out-of-range, shorted, open, or intermittent signal from the power steering pressure sensor circuit. MIL set and freeze-frame data recorded. Repair required to restore correct sensor input.
Repair difficulty: Medium
Diagnostic time: 0.5-2.0 hours
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