Toyota Power Steering Oil Pressure Switch

Description

Power Steering Switch (PSS)

The General function of the Power steering Switch (for the engine management system) is to monitor the increased hydraulic pressure that is created when the steering wheel is rotated or held in a steering assist position, to allow the PCM to adjust the engine RPM to compensate for the increased engine load. The 2-terminal pressure switch generally results in an ON/OFF operational state that is pressure activated.

Failure to correctly determine when the hydraulic pressure increases or decreases during a steering or non-steering manoeuvre may create an increased RPM condition at Idle due to overcompensation or intermittent engine stalling due to under compensation for the increased engine load.

This condition may result in a typical Fault Code logged.
Generally: P0551 – Power Steering Pressure Switch Circuit Range/Performance.

Testing Procedure (PSS)

A suitable scanner may be utilised to check the switch operation during increased and decreased pressure cycles as the steering wheel is rotated as required.

A multimeter can also be utilised at the switch to monitor the ON/OFF performance as the:

• Steering wheel again is rotated as required.
• Switch is in a closed position; an expected result should indicate an earthed reading. (as near as possible to 0.0V)
• When the switch is in an opened position, an expected result should indicate the full circuit reference voltage.