The PSP switch is a normally open switch, mounted in the pressure line between the steering gear and the power steering pump. When steering system pressure reaches a high-pressure setpoint, the power steering pressure switch closes and sends a signal to the PCM that the PCM uses to maintain engine idle speed during parking maneuvers. The PCM can detect switch problems and set trouble codes to indicate specific faults. Check the operation of the power steering pressure switch if the engine stalls during parking or if the engine idles continuously at high rpm. Performing the following test will set a diagnostic trouble code and illuminate the Check Engine light. Be prepared to clear the diagnostic trouble code after performing the tests and making the necessary repairs. Disconnect the power steering pressure switch connector and connect an ohmmeter to the terminals on the switch body. Start the engine and let it idle. Make sure the meter leads, loose clothing, long hair, etc. are away from the moving parts of the engine before starting the engine. Turn the steering wheel to point the front wheels straight ahead and read the ohmmeter. It should indicate an open circuit. Turn the steering wheel to either side and watch the ohmmeter. The power steering pressure switch should close as the wheel nears the steering stop on either side, and the meter should indicate continuity of close to zero ohms. If the switch fails either test, replace it. If the switch is OK, troubleshoot the engine idle control operation if high idle speed or stalling problems continue. Also check the wiring harness for an open circuit to the PCM or a damaged harness and check for continuity to ground on the black wire of the harness connector. Disconnect the electrical connector from the switch. Using a back-up wrench on the hex fitting, unscrew the switch from the junction block. Install and connect the new switch. Bleed air from the power steering system. Add fluid as required.