P0551

P0551-POWER STEERING PRESSURE SWITCH PERFORMANCE





For a complete wiring diagram refer to the Wiring Information Electrical Diagrams.

Theory of Operation

The power steering switch is used to enable quick spark and fuel corrections for high power steering loads to maintain target idle speed. The power steering switch rationality monitors the switch input during high vehicle speed conditions when the steering wheel cannot be turned far enough to reach the high-pressure switch point. If the power steering switch input remains at a high-pressure condition at high vehicle speeds, a failure timer will increment.

- When Monitored:
With the ignition key on and engine running.

- Set Condition:
With the vehicle above 40 mph for over 30 seconds, the power steering pressure switch remains open. Two Trip Fault. Three good trips to turn off the MIL.





WARNING: On vehicles equipped with the high voltage system, you must thoroughly read and follow all High Voltage Safety procedures. In addition, before performing any diagnostic or service procedure near a high voltage component, you must perform the High Voltage Power Down. Failure to follow these instructions may result in possible serious or fatal injury

Always perform the Pre-Diagnostic Troubleshooting procedure before proceeding. Pre-Diagnostic Troubleshooting Procedure.

1. ACTIVE DTC
1. Start the engine and allow it to reach normal operating temperature.

WARNING: When the engine is operating, do not stand in direct line with the fan. Do not put your hands near the pulleys, belts or fan. Do not wear loose clothing. Failure to follow these instructions may result in possible serious or fatal injury.

NOTE: Diagnose and repair any system voltage DTCs before continuing with this test.

2. With the scan tool, select View DTCs.

Is the DTC Active at this time?

Yes

- Go To 2

No

- Refer to the INTERMITTENT CONDITION Diagnostic Procedure. Intermittent Condition Test.

2. POWER STEERING PRESSURE SWITCH




1. Turn the ignition off.
2. Disconnect the Power Steering Pressure Switch harness connector.
3. Ignition on, engine not running.
4. Connect a jumper wire to the (K66) P/S Switch Signal circuit at the harness connector.
5. Use the scan tool to monitor the Power Steering Pressure Switch status.
6. Touch the other end of the jumper wire to the (Z988) Ground circuit at the Power Steering Pressure Switch harness connector several times.

Did the Power Steering Pressure Switch status change from High to Low when connecting and disconnecting the jumper wire?

Yes

- Replace the Power Steering Pressure Switch.
- Perform the POWERTRAIN VERIFICATION TEST. Powertrain Verification Test.

No

- Go To 3 NOTE: Remove the jumper wire before continuing.


3. (K66) P/S SWITCH SIGNAL CIRCUIT OPEN




1. Turn the ignition off.
2. Disconnect the C3 PCM harness connector.

CAUTION: Do not probe the PCM harness connectors. Probing the PCM harness connectors will damage the PCM terminals resulting in poor terminal to pin connection. Install PCM Pinout Box 8815 to perform diagnosis.

3. Measure resistance of (K66) P/S Switch Signal circuit from the Power Steering Pressure Switch harness connector to the appropriate terminal of special tool #8815.

Is the resistance below 5.0 ohms?

Yes

- Go To 4

No

- Repair the open in the (K66) P/S Switch Signal circuit.
- Perform the POWERTRAIN VERIFICATION TEST. Powertrain Verification Test.

4. (K66) P/S SWITCH SIGNAL CIRCUIT SHORTED TO GROUND




1. Measure the resistance between ground and the (K66) P/S Switch Signal circuit in the Switch connector.

Is the resistance below 100 ohms?

Yes

- Repair the short to ground in the (K66) P/S Switch Signal circuit.
- Perform the POWERTRAIN VERIFICATION TEST. Powertrain Verification Test.

No

- Go To 5

5. (Z988) GROUND CIRCUIT OPEN




1. Measure the resistance between Ground and the (Z988) Ground circuit in the Power Steering Pressure Switch connector.

Is the resistance below 100 ohms?

Yes

- Go To 6

No

- Repair the open in the (Z988) Ground circuit.
- Perform the POWERTRAIN VERIFICATION TEST. Powertrain Verification Test.

6. POWERTRAIN CONTROL MODULE (PCM)

NOTE: Before continuing, check the PCM harness connector terminals for corrosion, damage, or terminal push out. Repair as necessary.

1. Using the schematics as a guide, inspect the wire harness and connectors. Pay particular attention to all Power and Ground circuits.

Were there any problems found?

Yes

- Repair as necessary.
- Perform the POWERTRAIN VERIFICATION TEST. Powertrain Verification Test.

No

- Replace and program the Powertrain Control Module.
- Perform the POWERTRAIN VERIFICATION TEST. Powertrain Verification Test.