Power Steering Pressure Switch: Testing and Inspection

ECM Input E.7.8:

DFI Emission Sensor Circuit:

DESCRIPTION:

The Power Steering switch 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 CKT 639 and sends the 12 volt signal to the ECM on CKT 495. When high power steering pressures occur, the switch opens and CKT 495 voltage is read by the ECM as 0 volts.

The ECM uses the power steering input to extend the ISC motor when high power steering pressures occur at low speeds, such as during parking maneuvers.

NOTES ON FAULT TREE:

1. Checking ECM and circuits ability to respond to cycling CKT 495.

2. Checking for open power steering switch or switch connector. If E.7.8 passes, the ECM and wiring are OK.

3. Checking for 12 volts present on CKT 639.

4. Checking for ECM able to recognize a signal on terminal D8.

5. If 15A fuse is blown, check for CKT 495 or 639 shorted to ground.

NOTE ON INTERMITTENTS:

At key on, probe ECM terminal D8 with a voltmeter to ground. Manipulate wiring and connectors while observing voltmeter. If voltage drops to 0 volts at key "ON" engine "OFF" repair open or short to ground.