Power Steering Pressure Switch Check

Power Steering Pressure Switch (PSPS) Diagnosis:

Power Steering Pressure Switch (PSPS) Circuit:

Circuit Description
The Power Steering Pressure Switch (PSPS) is normally open to ground, and CKT 495 will be near battery voltage.

Turning the steering wheel increases power steering oil pressure and creates a 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 PCM will increase the idle speed, retard the timing and disengage the Ai C on manual transmission vehicles only. On 1994 automatic vehicles (S Pickup) the switch will not be installed and the wiring will be physically on the vehicle but will be inoperative.

Chart Test Description
Number(s) below refer to circled number(s) on the diagnostic chart.

1. Checks for PCM 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.

Diagnostic Aids
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 CKT 495 shorted to ground, will cause timing to retard at idle, and may affect idle quality.