P0089

CIRCUIT DESCRIPTION
The Engine Control Module (ECM) uses commanded fuel pump flow to determine a desired fuel rail pressure. The actual fuel pressure is monitored using the Fuel Rail Pressure (FRP) sensor. If the fuel rail pressure sensor indicates a pressure more than 20 MPa greater than desired, Diagnostic Trouble Code (DTC) P0089 will set.

CONDITIONS FOR RUNNING THE DTC
^ DTC P0192, P0193, or P1635 are not set.
^ The ignition is ON.

CONDITIONS FOR SETTING THE DTC
^ The difference between actual and desired fuel rail pressure is more than 20 MPa.
^ Commanded fuel pump flow is 100 cubic mm/second or less.

ACTION TAKEN WHEN THE DTC SETS
^ The control module illuminates the Malfunction Indicator Lamp (MIL) when the diagnostic runs and fails.
^ The control module records the operating conditions at the time the diagnostic fails. The control module stores this information in the Freeze Frame/Failure Records.

CONDITIONS FOR CLEARING THE MIL/DTC
^ The control module turns OFF the Malfunction Indicator Lamp (MIL) after 3 consecutive ignition cycles that the diagnostic runs and does not fail.
^ A current DTC, Last Test Failed, clears when the diagnostic runs and passes.
^ A history DTC clears after 40 consecutive warm-up cycles, if no failures are reported by this or any other emission related diagnostic.
^ Use a scan tool in order to clear the MIL and the DTC.

TEST DESCRIPTION

Steps 1-10:

The numbers below refer to the step numbers on the diagnostic table.
2. DTC P0090 is a current flow problem in the fuel rail pressure regulator circuit. This incorrect current draw could lead to incorrect fuel pressure. This hardware problem should be diagnosed before the performance DTC is checked.
3. DTC P0093 indicates a major leak in the fuel system. All fuel leaks and electrical circuit faults must be diagnosed before the performance DTC is checked.
5. If the fuel system vacuum is below 5 in Hg, there is no supply-side restriction.
7. The fuel filter is difficult to inspect for restrictions, so it must be replaced as a possible cause of this DTC.
8. When the fuel filter is eliminated, the fuel system must be inspected for damaged lines. This condition could be from road damage, from corrosion, or from an obstruction in the fuel lines.