Seville V8-273 4.5L (1989)
Power Steering Pressure Switch: Description and Operation
Power Steering Pressure Switch
The power steering pressure switch is normally closed. The power steering switch opens with power steering pump pressure. The power steering
pressure switch receives 12 volts from the 10 amp solenoid fuse, located in the relay center. When high power steering pressure occurs, the switch
contacts are opened by power steering oil pressure. The Electronic Control Module (ECM) will read zero volts on the signal line leading from the switch
to the ECM. The ECM uses the power steering switch input to extend the Idle Speed Control (ISC) solenoid when high power steering loads occur, in
order to help maintain idle speed. Input switch test code EI78 can be used to check the power steering pressure switch for proper operation.
