P0550

Circuit Description
The Power Steering Pressure (PSP) switch is a normally closed switch which opens when power steering pressure exceeds 450 to 650 psi. The PSP switch closes again when pressure drops below 100 to 450 psi. The PCM pulls the PSP signal circuit up to approximately 12 volts. This diagnostic test monitors the voltage on the PSP switch signal circuit. During power steering no-load condition, the PSP switch is closed causing the signal voltage to be pulled low. When a load is placed on the power steering such as during low speed parking maneuvers or at full steering lock, the switch opens and the PCM will detect 12 volts on the signal circuit. The PCM uses this information to adjust idle speed when the additional load is present.

Conditions for Running the DTC
^ Engine running.
^ Vehicle speed 45 MPH or greater.

Conditions for Setting the DTC
PSP signal voltage high for 60 seconds.

Action Taken When the DTC Sets
^ The PCM stores the DTC information into memory when the diagnostic runs and fails.
^ The Malfunction Indicator Lamp (MIL) will not illuminate.
^ The PCM records the operating conditions at the time the diagnostic fails. The PCM stores this information in the Failure Records.

Conditions for Clearing the MIL/DTC
^ A History DTC will clear after forty consecutive warm-up cycles, if no failures are reported by this or any Other non-emission related diagnostic.
^ A last test failed (Current DTC) will clear when the diagnostic runs and does not fail.
^ Use a scan tool in order to clear the MIL/DTC.
^ Interrupting the PCM battery voltage may or may not clear DTCs. This practice is not recommended.

Diagnostic Aids

Notice: Use the Connector Test Adapter Kit J 35616-A for any test that requires probing the following items:
^ The PCM harness connectors
^ The electrical center fuse/relay cavities
^ The component terminals
^ The component harness connector
Using this kit will prevent damage caused by the improper probing of connector terminals.
Check for intermittent contact at the power steering pressure switch. Engine torque/movement stretching the harness could be causing an intermittent open circuit.


Test Description
Number(s) below refer to the step number(s) on the Diagnostic Table.
2. This is a functional test of the switch. This DTC only detects high signal voltage (open signal or ground circuits, switch stuck open). If the display always indicates Normal, check for the signal circuit shorted to ground or a stuck closed switch.
3. If display always says Hi Press., proceed with circuit diagnosis. If the display indicates Hi Press. With the engine running, and Normal with the key on, engine oft, with no steering load, there may be a problem causing excessive pressure in the power steering system.