Power Steering Pressure Switch
WARNING: This page is about a different car, the 2002 Mercury Villager. However, it is still accessible from the selected car via links, so may be relevant.
The Power Steering Pressure (PSP) switch monitors power steering pressure. When power steering fluid pressure exceeds the preset limit, the PSP switch sends an input signal to the PCM. The PCM then adjusts idle speed. PSP switch is located in power steering pump.