P0551-POWER STEERING PRESSURE SWITCH PERFORMANCE
For a complete wiring diagram Refer to Section 8W.
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.
| Possible Causes |
| (K66) P/S SWITCH SIGNAL CIRCUIT OPEN |
| (K66) P/S SWITCH SIGNAL CIRCUIT SHORTED TO GROUND |
| (Z988) GROUND CIRCUIT OPEN |
| POWER STEERING PRESSURE SWITCH |
| PCM |
Always perform the Pre-Diagnostic Troubleshooting procedure before proceeding. (Refer to 9 - ENGINE - DIAGNOSIS AND TESTING).
Diagnostic Test
1. ACTIVE DTCStart the engine.
Allow the engine to reach normal operating temperature.
With a scan tool, select View DTCs.
NOTE: It may be necessary to drive the vehicle to meet the conditions to set this DTC, try to repeat the conditions in which the fault originally set by reviewing the Freeze Frame data.
Is the DTC Active or Pending at this time?
Yes
- Go To 2
No
- Refer to the INTERMITTENT CONDITION Diagnostic Procedure.
- Perform the POWERTRAIN VERIFICATION TEST. (Refer to 9 - ENGINE - STANDARD PROCEDURE)
2. POWER STEERING PRESSURE SWITCH
Turn the ignition off.
Disconnect the Power Steering Pressure Switch harness connector.
Ignition on, engine not running.
Connect a jumper wire to the (K66) P/S Switch Signal circuit at the harness connector.
Use the scan tool to monitor the Power Steering Pressure Switch status.
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. (Refer to 9 - ENGINE - STANDARD PROCEDURE)
No
- Go To 3
NOTE: Remove the jumper wire before continuing.
3. (K66) P/S SWITCH SIGNAL CIRCUIT OPEN
Turn the ignition off.
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 Miller Special Tool #8815 to perform diagnosis.
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. (Refer to 9 - ENGINE - STANDARD PROCEDURE)
4. (K66) P/S SWITCH SIGNAL CIRCUIT SHORTED TO GROUND
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. (Refer to 9 - ENGINE - STANDARD PROCEDURE)
No
- Go To 5
5. (Z988) GROUND CIRCUIT OPEN
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. (Refer to 9 - ENGINE - STANDARD PROCEDURE)
6. PCM
NOTE: Before continuing, check the PCM harness connector terminals for corrosion, damage, or terminal push out. Repair as necessary.
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. (Refer to 9 - ENGINE - STANDARD PROCEDURE)
No
- Replace and program the Powertrain Control Module per Service Information.
- Perform the POWERTRAIN VERIFICATION TEST. (Refer to 9 - ENGINE - STANDARD PROCEDURE)