Circuit Description
The engine control module (ECM) monitors fuel rail pressure (FRP) using the FRP sensor. If the sensor indicates a pressure more than the commanded rail pressure plus a possible transitional overshoot, the ECM will set diagnostic trouble code (DTC) P0088 for fuel rail pressure too high.
Conditions for Running the DTC
| • | DTCs P0192, P0193, or P0641 are not set. |
| • | The ignition is ON. |
Conditions for Setting the DTC
The actual fuel pressure is more than 167 MPa.
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. |
| • | The control module will limit fuel injection and fuel rail pressure. |
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. |
| • | Clear the MIL and the DTC with a scan tool. |
Diagnostic Aids
There are no driveability concerns associated with the fuel rail pressure regulator unless a DTC is present. The most likely cause of this DTC is a sticking fuel rail pressure regulator.
If the fuel system pressure is actually too high, a fuel knock and smoke condition will exist.
Test Description
The number below refers to the step number on the diagnostic table.
Step | Action | Values | Yes | No | ||||
|---|---|---|---|---|---|---|---|---|
Schematic Reference: Engine Controls Schematics | ||||||||
1 | Did you perform the Diagnostic System Check - Engine Controls? | -- | Go to Step 2 | |||||
2 |
Is the Actual Fuel Rail Pressure parameter within the specified range? | 1-1.8 MPa | Go to Step 3 | Go to Step 6 | ||||
Did DTC P0090 also set? | -- | Go to DTC P0090 | Go to Step 4 | |||||
4 |
Is the Actual Fuel Rail Pressure more than the specified value? | 167 MPa | Go to Step 11 | Go to Step 5 | ||||
5 |
Does the fuel pressure increment and stabilize through the entire fuel pressure range, with actual and desired fuel pressure within 2 MPa of each other at every fuel pressure? | -- | Go to Diagnostic Aids | Go to Step 11 | ||||
6 |
Does the Actual Fuel Rail Pressure measure more than the specified value? | 175 MPa | Go to Step 9 | Go to Step 7 | ||||
7 | Test the FRP sensor signal circuit for a short to ground. Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you find and correct the condition? | -- | Go to Step 12 | Go to Step 8 | ||||
8 | Replace the engine control module. Refer to Engine Control Module Replacement . Did you complete the replacement? | -- | Go to Step 12 | -- | ||||
9 | Test the signal circuit of the FRP sensor for a high resistance or an open. Refer to Testing for Continuity and Wiring Repairs in Wiring Systems. Did you find and correct the condition? | -- | Go to Step 13 | Go to Step 10 | ||||
10 | Replace the FRP sensor. Refer to Fuel Injection Fuel Rail Fuel Pressure Sensor Replacement . Did you complete the replacement? | -- | Go to Step 12 | -- | ||||
11 | Replace the FRP regulator. Refer to Fuel Pressure Regulator Replacement . Did you complete the replacement? | -- | Go to Step 12 | -- | ||||
12 |
Does the DTC fail this ignition? | -- | Go to Step 2 | Go to Step 13 | ||||
13 | With a scan tool, observe the stored information, Capture Info. Does the scan tool display any DTCs that have not been diagnosed? | -- | System OK | |||||
