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

Chart C-1E, Power Steering Pressure Switch Diagnosis:

Power Steering Pressure Switch Circuit Diagram:

CIRCUIT DESCRIPTION
The Power Steering Pressure (PSP) switch is normally open to ground, and CKT 495 will be near the 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 disengage the A/C relay.
^ A pressure switch that will not close or an open CKT 495 or 450, may cause the engine to stall when power steering loads are high.
^ A switch that will not open, or a CKT 495 shorted to ground, may affect idle quality and will cause the A/C relay to be de-energized.


TEST DESCRIPTION
Numbers below refer to circled numbers on diagnostic chart.

1. Different "SCAN" tools may display switch status differently. Refer to manufacturers operating instructions for your specific type "SCAN" tool.

2. Checks for short to ground in signal circuit.

3. Simulates a closed switch (high power steering pressure).