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. This diagnostic test monitors the power steering pressure switch. When a load is placed on the power steering such as full lock, the switch opens. When driving over 45 mph, no load condition, the switch is closed. DTC P0550 sets when the vehicle is above 45 MPH and the power steering pressure switch signal is open.

Conditions for Running the DTC

^ Engine running.
^ Vehicle speed 45 MPH or greater.

Conditions for Setting the DTC

Power steering pressure switch open for 60 seconds.

Action Taken When the DTC Sets

PCM limits desired idle speed to a minimum of 800 RPM.

^ The Malfunction Indicator Lamp (MIL) will not illuminate.
^ The PCM will command a message to be displayed.
^ The PCM may record operating conditions at the time the diagnostic fails. This information will be stored in the Failure Records.

Conditions for Clearing the Message/DTC

^ The PCM will turn the message OFF after one run and pass of the diagnostic test.
^ A History DTC will clear after forty consecutive warm-up cycles with no failures of any non-emission related diagnostic test.
^ A Last Test Failed (current) DTC will clear when the diagnostic runs and does not fail.
^ Use a scan tool to clear DTCs.
^ Interrupting PCM battery voltage may or may not clear DTCs. This practice is not recommended.

Diagnostic Aids

Check for intermittent contact at the power steering pressure switch or stretching of the harness causing an intermittent open circuit.

Test Description

Number(s) below refer to the step number(s) on the Diagnostic Table.

2. Checking if switch will respond to pressure.
3. If display stays Hi Press., there is an open or short to ground in the circuitry.
4. Checking if the ignition feed circuit or fuse is open.
5. Checking if the power steering pressure switch is open. With switch bypassed, input should be Normal.
6. Checking if the power steering pressure switch input circuit is open or shorted to ground.