P0551

P0551-POWER STEERING PRESSURE SWITCH PERFORMANCE

WHEN MONITORED
With the ignition key on and engine running.

SET CONDITION
With the vehicle above 40 m.p.h. 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.

Diagnostic Test

1. ACTIVE DTC

Ignition on, engine not running.
With a scan tool, read DTCs.

Q: Is the DTC active at this time?

YES: Go To 2
NO: Refer to the INTERMITTENT CONDITION Diagnostic Procedure. Intermittent Condition
Perform the POWERTRAIN VERIFICATION TEST. Powertrain Verification Test




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 Power Steering Pressure Switch 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.

Q: 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

Turn the ignition off.
Disconnect the PCM harness connectors.

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.

Q: 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

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

Q: 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

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

Q: 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. 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.

Q: 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