Power Steering Pressure Switch: Testing and Inspection

Chart C-1E - Power Steering Pressure Switch (PSPS):

Wiring Diagram for Chart C-1E - Power Steering Pressure Switch (PSPS):

CHART C-1E - POWER STEERING PRESSURE SWITCH (PSPS)

Circuit Description:


The power steering pressure switch is normally open to ground, and CKT 495 will be near battery voltage. Turning the steering wheel increases power steering oil pressure and its load on an idling engine. The pressure switch will close before the load can cause an idle problem.

Closing the switch causes CKT 495 to read less than 1 volt. The ECM will increase the idle air rate and retard the timing.


^ A pressure switch that will not close or an open CKT 495 or 450 may cause the engine to stop when power steering loads are high.


^ A switch that will not open or a CKT 450 or 495 shorted to ground will cause timing to retard at idle and may effect idle quality.


Test Description: Numbers below refer to circled numbers on the diagnostic chart.

1. Checks for ECM signal voltage on CKT 495, and confirms that ground CKT 450 is OK.

2. Maximum resistance or infinity indicates an open switch.


3. Less than 1 ohm indicates that the switch is closed when the power steering pressure is high. Switch is OK.