Power Steering Pressure Switch (PSPS)
WARNING: This page is about a different car, the 1995 Mazda MX-5 Miata. However, it is still accessible from the selected car via links, so may be relevant.
Disconnect power steering pressure switch electrical connector. Connect ohmmeter to PSPS terminal and ground. Start engine, and operate it at idle. Turn steering wheel from side to side, and observe ohmmeter. Ohmmeter should indicate continuity when front wheels are turned. Continuity should not exist when wheels are not turned. Replace switch as necessary.