ECM Input E.7.8 - Power Steering Pressure Switch Circuit: Notes
WARNING: This page is about a different car, the 1989 Cadillac Fleetwood and 1989 Cadillac DeVille. However, it is still accessible from the selected car via links, so may be relevant.
The Power Steering Pressure Switch (PSPS) is normally closed and opens with high power steering pressure. During normal driving, the power steering switch receives 12 volts from the 15-amp solenoid fuse on circuit No. 639, and sends the 12-volt signal to ECM on circuit No. 495. When high power steering pressures occur, the switch opens and circuit No. 495 voltage is read by ECM as zero volts.
The ECM uses power steering input to extend the ISC motor when high power steering pressures occurs at low speeds, such as parking maneuvers.
NOTE:
Test numbers refer to test numbers on diagnostic chart.
- Checks ECM and circuits ability to respond to cycling circuit No. 495.
- Checks for open power steering switch or switch connector. If E.7.8 passes, ECM and wiring are okay.
- Checks for 12 volts present on circuit No. 639.
- Checks for ECM ability to recognize a signal on terminal D8.
- If 15-amp fuse is blown, check for circuits No. 495 or 639 shorted to ground.