Power Steering Pressure Switch: Description and Operation

PURPOSE
This switch tells the Electronic Control Module (ECM) that the vehicle is in a parking maneuver. The ECM uses this information to compensate for the additional engine load by moving the Idle Air Control (IAC) valve. The ECM will also turn "OFF" the A/C clutch when high pressure is detected.

OPERATION
The power steering pressure 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.