DTC P0551: Power Steering Pressure Sensor Circuit Range/Performance

CIRCUIT OPERATION
• A battery positive voltage is applied to the power steering pressure switch output terminal (terminal No. 1) from the ECM (terminal No. 37) <M/T> or PCM (terminal No. 52) <A/T> via the resistor in the ECM <M/T> or PCM <A/T>.
TECHNICAL DESCRIPTION
• The power steering pressure switch converts the existence of a power steering load into a high/low voltage, and inputs it into the ECM <M/T> or PCM <A/T>.
• When the steering wheel is turned, hydraulic pressure rises. The power steering pressure switch closes, and the applied battery positive voltage will be grounded. With this, the power steering pressure switch output voltage will fluctuate between 12 volts and 0 volt.
• While driving with the steering wheel held straight, the power steering pressure switch turns "OFF".
• The ECM <M/T> or PCM <A/T> checks whether the power steering pressure switch turns "OFF" or "ON" during driving.
DESCRIPTIONS OF MONITOR METHODS
• If the power steering pressure switch is constantly ON in spite of repeating the prescribed (stop-and-go) driving pattern, a malfunction is determined to have occurred.
MONITOR EXECUTION
Continuous
MONITOR EXECUTION CONDITIONS (Other monitor and Sensor)

Other Monitor (There is no temporary DTC stored in memory for the item monitored below)
• Not applicable

Sensor (The sensor below is determined to be normal)
• Engine coolant temperature sensor
DTC SET CONDITIONS Logic Flow Chart


Check Conditions
Engine coolant temperature is higher than 18°C (64°F).
Drive for 4 seconds or more with the vehicle speed is 50 km/h (31 mph) or more. Stop the vehicle [vehicle speed is 1.5 km/h (1 mph) or less]. Repeat 10 times or more.

Judgment Criteria
• Power steering pressure switch continues to be "ON".
OBD-II DRIVE CYCLE PATTERN
None.
TROUBLESHOOTING HINTS (The most likely causes for this code to be set are:
• Power steering pressure switch failed.
• Open or shorted power steering pressure switch circuit, or connector damage.
• ECM failed. <M/T>
• PCM failed. <A/T>