SFI SYSTEM, Diagnostic DTC:P0088

DTC Code DTC Name
P0088 Fuel Rail / System Pressure - Too High

DESCRIPTION

The high-pressure fuel system consists of the spill control valve, pump plunger, check valve, relief valve and fuel pressure sensor. The spill control valve opens and closes the low-pressure fuel line (from the fuel tank), the pump plunger (operated by the camshaft) pressurizes fuel, the check valve mechanically opens and closes the high pressure fuel line (to the fuel delivery pipe), the relief valve prevents fuel pressure from becoming extremely high, and the fuel pressure sensor located on the fuel delivery pipe monitors fuel pressure.

The fuel pump for high pressure is installed to the cylinder head cover (bank 1) and is driven by the cam located at the rear end of the exhaust camshaft.

The plunger moves up and down by the camshaft rotations, and produces a vacuum to suck fuel and pressurizes the fuel. This fuel then pushes the check valve open and flows into the fuel delivery pipe. The ECM opens and closes the spill control valve to regulate the fuel pressure to the target fuel pressure of 2 to 18 MPa (20.4 to 183.5 kgf/cm2, 290 to 2609 psi). In order to obtain and maintain the target pressure, the ECM monitors the fuel pressure using the fuel pressure sensor and performs the feedback control.

If the internal fuel pressure of the fuel delivery pipe exceeds the standard pressure of 25.0 MPa (255.0 kgf/cm2, 3626 psi), the fuel relief valve installed on gateway of the fuel delivery pipe discharges the fuel pressure and then returns the fuel back to the fuel tank.

DTC No. DTC Detection Condition Trouble Area
P0088

ECM did not command fuel pump for high pressure to open spill control valve, but fuel pressure increases 3 MPa (30.6 kgf/cm2, 435 psi) from target pressure for about 10 seconds

(1 trip detection logic)

  • Fuel pump for high pressure

  • ECM

MONITOR DESCRIPTION

If the fuel pressure does not decrease even after the ECM commands the high-pressure fuel pump to open the spill control valve, a DTC is output.

If there is minimal difference between the fuel pressure before and after the fuel relief valve operates, a DTC is output.

MONITOR STRATEGY

Required sensors/Components Fuel pressure sensor
Frequency of operation Continuous

CONFIRMATION DRIVING PATTERN


  1. Connect the GTS to the DLC3.

  2. Turn the power switch on (IG) and turn the GTS on.

  3. Record the Freeze Frame Data.

  4. Clear the DTCs (even if no DTCs are stored, perform the clear DTC procedure) Click here.

  5. Turn the power switch off and wait for at least 30 seconds.

  6. Turn the power switch on (IG) and turn the GTS on.

  7. Based on engine speed, engine load and other freeze frame data stored in the ECM, reproduce the conditions present when the DTC was stored.

  8. Enter the following menus: Powertrain / Engine and ECT / Trouble Codes.

  9. Read the DTC.

    Tech Tips


    • If a DTC is output, the system is malfunctioning.

    • If a DTC is not output, perform the following procedure.

  10. Enter the following menus: Powertrain / Engine and ECT / Utility / All Readiness.

  11. Input the DTC: P0088.

  12. Check the DTC judgment result.

    GTS Display Description
    NORMAL

    • DTC judgment completed

    • System normal
    ABNORMAL

    • DTC judgment completed

    • System abnormal
    INCOMPLETE

    • DTC judgment not completed

    • Perform driving pattern after confirming DTC enabling conditions
    N/A

    • Unable to perform DTC judgment

    • Number of DTCs which do not fulfill DTC preconditions has reached ECU's memory limit

    Tech Tips


    • If the judgment result shows ABNORMAL, the system has a malfunction.

    • If the judgment result shows NORMAL, the system is normal.

INSPECTION PROCEDURE

Tech Tips

Read freeze frame data using the GTS. The ECM records vehicle and driving condition information as freeze frame data the moment a DTC is stored. When troubleshooting, freeze frame data can be helpful in determining whether the vehicle was moving or stationary, whether the engine was warmed up or not, whether the air fuel ratio was lean or rich, as well as other data recorded at the time of a malfunction.

PROCEDURE


  1. CHECK OTHER DTCS OUTPUT (IN ADDITION TO DTC P0088)


    1. Connect the GTS to the DLC3.

    2. Turn the power switch on (IG) and turn the GTS on.

    3. Enter the following menus: Powertrain / Engine and ECT / Trouble Codes.

    4. Read the DTCs.

      Result
      Result Proceed to
      DTC P0088 is output A
      DTC P0088 and other DTCs are output B

      Tech Tips

      If any DTCs other than P0088 are output, troubleshoot those DTCs first.


    B

    GO TO DTC CHART Click here

    A

  2. PERFORM ACTIVE TEST USING GTS


    1. Connect the GTS to the DLC3.

    2. Start the engine and turn the GTS on.

    3. Enter the following menus: Powertrain / Engine and ECT / Active Test / Control the Target Fuel Press / Fuel Press.

    4. Check that the fuel pressure fluctuates when the target fuel pressure changes.

      Tech Tips

      The Active Test operation lowers the target fuel pressure by 12.5% or increase the target fuel pressure by 24.8%.

      OK
      Fuel pressure fluctuates.

    NG

    REPLACE FUEL PRESSURE SENSOR Click here

    OK

  3. REPLACE FUEL PUMP ASSEMBLY (FOR HIGH PRESSURE)


    1. Replace the fuel pump assembly (for high pressure) Click here.


    NEXT

  4. CHECK IF DTC OUTPUT RECURS (SEE IF DTC P0088 IS OUTPUT AGAIN)


    1. Connect the GTS to the DLC3.

    2. Turn the GTS on.

    3. Clear the DTCs Click here.

    4. Drive the vehicle in accordance with the driving pattern described in the Confirmation Driving Pattern.

    5. Enter the following menus: Powertrain / Engine and ECT / Trouble Codes.

    6. Read the DTCs.

      Result
      Result Proceed to
      DTC P0088 is output A
      DTC is not output B

    B

    END

    A

    REPLACE ECM Click here