Circuit Description

Power Steering Pressure (PSP) switch is normally open to ground, and PCM terminal will be near battery voltage. Turning steering wheel increases power steering oil pressure and its load on an idling engine. PSP switch will close before load can cause a poor idling condition. Closing PSP switch causes PCM voltage signal to read less than one volt. PCM will increase throttle valve opening to maintain adequate idle speed to prevent engine load stall.