ECD SYSTEM(for DPF), Diagnostic DTC:P0234, P1251

DTC Code DTC Name
P0234 Turbocharger / Supercharger Overboost Condition
P1251 Turbocharger / Supercharger Overboost Condition (Too High)

DESCRIPTION

DTC No. Detection Item DTC Detection Condition Trouble Area MIL Memory
P0234 Turbocharger / Supercharger Overboost Condition

Actual turbocharger pressure "MAP" deviates by 30 kPa (225 mmHg, 8.9 in.Hg) or higher from the simulated target pressure "Target Booster Pressure" for 100 seconds at an engine speed of 2400 to 4000 rpm.

(1 trip detection logic)

  • Vacuum regulating valve assembly (for turbocharger control)

  • Open or short in vacuum regulating valve assembly (for turbocharger control) circuit

  • Turbocharger sub-assembly

  • Electric EGR control valve assembly

  • Manifold absolute pressure sensor

  • ECM

 Comes on DTC stored
P1251 Turbocharger / Supercharger Overboost Condition (Too High)

The turbocharger pressure is 300 kPa (2250 mmHg, 89 in.Hg) or more for 5 seconds or more at an engine speed of 2000 to 4000 rpm.

(1 trip detection logic)

  • Vacuum regulating valve assembly (for turbocharger control)

  • Open or short in vacuum regulating valve assembly (for turbocharger control) circuit

  • Turbocharger sub-assembly

  • Electric EGR control valve assembly

  • Manifold absolute pressure sensor

  • ECM

 Comes on DTC stored

Tech Tips


  • If DTC P0234 or P1251 is stored, the following symptoms may appear.

    When the nozzle vane of the turbocharger is stuck closed:


    • Vehicle surge when driving with full load

    • Low power output due to ECM limiting power output

Related Data List
DTC No. Data List
P0234

  • MAP

  • Target Booster Pressure

  • MAF

  • Target EGR Position

  • Actual EGR Valve Pos.

  • VN Turbo Command

  • Atmosphere Pressure
P1251

CONFIRMATION DRIVING PATTERN

DTC No. DTC Detection Drive Pattern
P0234 After warming up the engine, the vehicle is driven at a constant vehicle speed at an engine speed of 2400 rpm or more for 2 minutes
P1251 After warming up the engine, fully depress the accelerator pedal for 5 seconds or more so that the engine speed is 2400 rpm or more.

WIRING DIAGRAM

Refer to DTC P0045 Click here.

CAUTION / NOTICE / HINT

Note


  • Inspect the fuses of circuits related to this system before performing the following inspection procedure.

  • After replacing the ECM, the new ECM needs registration (Click here ) and initialization Click here.

PROCEDURE


  1. READ DTC OUTPUT (RECORD STORED DTC AND FREEZE FRAME DATA)


    1. Connect the GTS to the DLC3.

    2. Turn the ignition switch to ON and turn the GTS on.

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


      Powertrain > Engine > Trouble Codes

    4. Record the stored DTC and Freeze Frame Data.

      Tech Tips

      Be sure to carefully examine "MAP" and "Target Booster Pressure" in the freeze frame data.

      Result
      Proceed to
      NEXT

    NEXT

  2. CHECK ANY OTHER DTCS OUTPUT (IN ADDITION TO DTC P0234 AND/OR P1251)


    1. Connect the GTS to the DLC3.

    2. Turn the ignition switch to ON and turn the GTS on.

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


      Powertrain > Engine > Trouble Codes

    4. Read the DTCs.

      Result
      Proceed to
      DTC P0234 and/or P1251 are output
      DTC P0234 and/or P1251 and other DTCs are output

      Tech Tips

      If DTCs other than P0234 and/or P1251 are output, perform troubleshooting for those DTCs first.


    DTC P0234 and/or P1251 and other DTCs are output

    GO TO DTC CHART Click here

    DTC P0234 and/or P1251 are output

  3. READ VALUE USING GTS (MAP AND TARGET BOOSTER PRESSURE)


    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 / Data List / MAP and Target Booster Pressure.


      Powertrain > Engine > Data List
      Tester Display
      MAP
      Target Booster Pressure

    4. Take a snapshot when the engine speed is maintained at 4500 rpm with no load.

    5. Read the values of "MAP" and "Target Booster Pressure" in the Data List using the snapshot review function.

      Result
      Result Proceed to
      Difference between MAP and Target Booster Pressure is +/-15 kPa or higher A
      Except above B

    B

    CONFIRM WHETHER MALFUNCTION HAS BEEN SUCCESSFULLY REPAIRED Click here

    A

  4. CHECK AIR INTAKE SYSTEM


    1. Check for air leaks and blockages between the air cleaner case and turbocharger sub-assembly, and between turbocharger sub-assembly and intake manifold.

      Result
      Proceed to
      Leaks and/or blockages exist in the intake system
      No leaks and/or blockages in the intake system

      Tech Tips


      • Inspect the air intake system, especially hoses and pipes between the air cleaner assembly and turbocharger sub-assembly.

      • Check for abnormal disconnections, pipe and hose squashing, and any damage in the intake system.

      • Using your hand, check whether the pipes and hoses in the intake system are securely connected.

      • By applying soapy water and revving up the engine, air leaks from the intake system can be checked by checking for bubbles.

      • Check for any modifications in the intake system made by the user.

      • Check if the vacuum hose for the manifold absolute pressure sensor is disconnected.


    No leaks and/or blockages in the intake system

    GO TO STEP 7 Click here

    Leaks and/or blockages exist in the intake system

  5. REPAIR OR REPLACE AIR INTAKE SYSTEM

    Result
    Proceed to
    NEXT

    NEXT

  6. READ VALUE USING GTS (MAP AND TARGET BOOSTER PRESSURE)


    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 / Data List / MAP and Target Booster Pressure.


      Powertrain > Engine > Data List
      Tester Display
      MAP
      Target Booster Pressure

    4. Take a snapshot when the engine speed is maintained at 4500 rpm with no load.

    5. Read the values of "MAP" and "Target Booster Pressure" in the Data List using the snapshot review function.

      Result
      Result Proceed to
      Difference between MAP and Target Booster Pressure is +/-15 kPa or higher A
      Except above B

    B

    GO TO STEP 27 Click here

    A

  7. CHECK CONNECTION OF VACUUM HOSE


    1. Check the turbocharger system vacuum hose connections.

      Result
      Proceed to
      OK
      NG

    NG

    REPAIR OR REPLACE VACUUM HOSE Click here

    OK

  8. INSPECT VACUUM REGULATING VALVE ASSEMBLY (FOR TURBOCHARGER CONTROL)


    1. Inspect the vacuum regulating valve assembly (for turbocharger control).

      Click here

      Result
      Proceed to
      OK
      NG

    NG

    REPLACE VACUUM REGULATING VALVE ASSEMBLY (FOR TURBOCHARGER CONTROL) Click here

    OK

  9. CHECK TURBOCHARGER SUB-ASSEMBLY


    1. Check the turbocharger sub-assembly.

      Click here

      Result
      Proceed to
      OK
      NG

    NG

    REPLACE TURBOCHARGER SUB-ASSEMBLY Click here

    OK

  10. CHECK HARNESS AND CONNECTOR (VACUUM REGULATING VALVE ASSEMBLY (FOR TURBOCHARGER CONTROL) - ECM)


    1. Disconnect the vacuum regulating valve assembly (for turbocharger control) connector.

    2. Disconnect the ECM connector.

    3. Measure the resistance according to the value(s) in the table below.

      Standard Resistance
      Tester Connection Condition Specified Condition
      B43-2 - B76-83 (VN) Always Below 1 Ω
      B43-2 or B76-83 (VN) - Body ground Always 10 kΩ or higher

    4. Reconnect the vacuum regulating valve assembly (for turbocharger control) connector.

    5. Reconnect the ECM connector.

      Result
      Proceed to
      OK
      NG

    NG

    REPAIR OR REPLACE HARNESS OR CONNECTOR Click here

    OK

  11. CHECK DIESEL THROTTLE BODY ASSEMBLY


    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 / Data List / Actual Throttle Position.


      Powertrain > Engine > Data List
      Tester Display
      Actual Throttle Position

    4. Take a snapshot when accelerating with the accelerator fully depressed.

    5. Read the value of "Actual Throttle Position" in the Data List using the snapshot review function.

      Result
      The value for "Actual Throttle Position" is 0%.
      Result
      Proceed to
      OK
      NG

    NG

    REPLACE DIESEL THROTTLE BODY ASSEMBLY Click here

    OK

  12. CHECK ELECTRIC EGR CONTROL VALVE ASSEMBLY


    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 / Data List / Actual EGR Valve Pos.


      Powertrain > Engine > Data List
      Tester Display
      Actual EGR Valve Pos.

    4. Take a snapshot when accelerating with the accelerator fully depressed.

    5. Read the value of "Actual EGR Valve Pos." in the Data List using the snapshot review function.

      Result
      The value for "Actual EGR Valve Pos." is 0%.
      Result
      Proceed to
      OK
      NG

    NG

    REPLACE ELECTRIC EGR CONTROL VALVE ASSEMBLY Click here

    OK

  13. PERFORM ACTIVE TEST USING GTS (ACTIVATE THE VSV FOR EGR COOLER BYPASS)


    1. Connect the GTS to the DLC3.

    2. Start the engine and warm it up, and make sure the A/C switch and all accessory switches are off.

    3. Turn the ignition switch off and wait for 30 seconds.

    4. Start the engine and turn the GTS on.

    5. Enter the following menus: Powertrain / Engine and ECT / Data List / MAF.


      Powertrain > Engine > Data List
      Tester Display
      MAF

    6. Read the MAF value displayed on the tester while the engine is idling.

    7. Enter the following menus: Powertrain / Engine and ECT / Active Test / Activate the VSV for EGR Cooler Bypass / Data List / EGR Cooler Bypass Position and MAF.

      Tech Tips

      Whether the EGR is passing through the bypass side or cooler side during the Active Test can be confirmed by checking EGR Cooler Bypass Position.


      Powertrain > Engine > Active Test
      Active Test Display
      Activate the VSV for EGR Cooler Bypass
      Data List Display
      MAF
      EGR Cooler Bypass Position

    8. Using the Active Test function, switch the EGR valve bypass switching valve between "Cooler" and "Bypass" a few times, and then check whether the MAF value changes after switching the valve from "Cooler" to "Bypass".

      Tech Tips

      If idling continues for 20 minutes or more, the EGR valve target opening angle becomes 0% (EGR valve fully closed). As this makes diagnosis impossible, it becomes necessary to drive the vehicle or restart the engine.

      Result
      Tester Display Result Proceed to
      Activate the VSV for EGR Cooler Bypass: Cooler to Bypass MAF value does not change A
      MAF value changes B

      Tech Tips

      If the EGR cooler is clogged, the mass air flow changes.


    B

    REPLACE EGR PIPE WITH COOLER SUB-ASSEMBLY Click here

    A

  14. READ VALUE USING GTS (INJECTION FEEDBACK VAL #1 TO #4)


    1. Connect the GTS to the DLC3.

    2. Turn the ignition switch to ON and turn the GTS on.

    3. Start the engine and warm it up.

    4. Enter the following menus: Powertrain / Engine and ECT / Data List / Injection Feedback Val #1 to #4.


      Powertrain > Engine > Data List
      Tester Display
      Injection Feedback Val #1
      Injection Feedback Val #2
      Injection Feedback Val #3
      Injection Feedback Val #4

    5. Read the values.

      Standard Value
      Item Engine Speed* Reference Value
      Injection Feedback Val #1 to #4 Idling

      -3.0 to 3.0 mm3/st

      Tech Tips


      • *: The A/C switch and all accessory switches should be off, and the engine should be fully warmed up.

      • When the values are outside the standard range, deposits inside the injector assemblies may be causing the problem.

      OK
      Values are within the standard range.
      Result
      Proceed to
      OK
      NG

    NG

    REPLACE INJECTOR ASSEMBLY OF MALFUNCTIONING CYLINDER Click here

    OK

  15. CHECK ANY OTHER DTCS OUTPUT (IN ADDITION TO DTC P0234 AND/OR P1251)


    1. Connect the GTS to the DLC3.

    2. Turn the ignition switch to ON.

    3. Turn the GTS ON.

    4. Clear the DTCs.


      Powertrain > Engine > Clear DTCs

    5. Turn the ignition switch off and wait for 30 seconds or more.

    6. Start the engine and warm it up for 1 minute or more.

    7. Turn the GTS ON.

    8. Read the value of Engine Speed from the Freeze Frame Data recorded previously.

      Tech Tips

      When performing the DTC detection drive pattern, make sure the engine speed increases to 2400 rpm or more and exceeds the "Engine Speed" value from the freeze frame data.

    9. After warming up the engine, drive the vehicle at a constant vehicle speed at an engine speed of 2400 rpm or more for 2 minutes.

    10. With the engine warmed up, fully depress the accelerator pedal for 5 seconds or more so that the engine speed is 2400 rpm or more.

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


      Powertrain > Engine > Trouble Codes

    12. Read the DTC.

      Result
      Proceed to
      DTC is not output
      DTC P0234 and/or P1251 is output

    DTC is not output

    END

    DTC P0234 and/or P1251 is output

    REPLACE ECM Click here

  16. REPLACE DIESEL THROTTLE BODY ASSEMBLY


    1. Replace the diesel throttle body assembly.

      Click here

      Result
      Proceed to
      NEXT

    NEXT

    GO TO STEP 27 Click here

  17. REPLACE EGR PIPE WITH COOLER SUB-ASSEMBLY


    1. Replace the EGR pipe with cooler sub-assembly.

      Click here

      Result
      Proceed to
      NEXT

    NEXT

    GO TO STEP 27 Click here

  18. REPLACE ECM


    1. Replace the ECM.

      Click here

      Result
      Proceed to
      NEXT

    NEXT

    GO TO STEP 27 Click here

  19. REPAIR OR REPLACE HARNESS OR CONNECTOR


    1. Repair or replace the harness or connector.

      Result
      Proceed to
      NEXT

    NEXT

    GO TO STEP 27 Click here

  20. REPLACE ELECTRIC EGR CONTROL VALVE ASSEMBLY


    1. Replace the electric EGR control valve assembly.

      Click here

      Result
      Proceed to
      NEXT

    NEXT

    GO TO STEP 27 Click here

  21. REPLACE INJECTOR ASSEMBLY OF MALFUNCTIONING CYLINDER


    1. Replace the injector assembly.

      Click here

      Note


      • When replacing the injector assembly for a cylinder, always be sure to use a new injection pipe.

      • Follow the procedure in the repair manual and temporarily install the injection pipes and nozzle leakage pipe, and then correctly position the injector assemblies. After that, tighten parts according to the torque specifications.

      • If the installation procedure is not performed correctly, injector assemblies may become out of position, which may cause the injector assemblies to deteriorate, resulting in malfunctions.

      • If an injector assembly deteriorates and malfunctions, other problems such as knocking, rough idle, etc. may occur.

      • If an injector assembly becomes out of position, it is possible that the seal between the injector assembly and injection pipe may become incomplete, resulting in a fuel leak.

      Result
      Proceed to
      NEXT

    NEXT

  22. BLEED AIR FROM FUEL SYSTEM


    1. Bleed the air from the fuel system.

      Click here

      Result
      Proceed to
      NEXT

    NEXT

  23. REGISTER INJECTOR COMPENSATION CODE AND PERFORM PILOT QUANTITY LEARNING


    1. Register the injector compensation code.

      Click here

    2. Perform the injector pilot quantity learning.

      Click here

      Result
      Proceed to
      NEXT

    NEXT

    GO TO STEP 27 Click here

  24. REPLACE TURBOCHARGER SUB-ASSEMBLY


    1. Replace the turbocharger sub-assembly.

      Click here

      Result
      Proceed to
      NEXT

    NEXT

    GO TO STEP 27 Click here

  25. REPLACE VACUUM REGULATING VALVE ASSEMBLY (FOR TURBOCHARGER CONTROL)


    1. Replace the vacuum regulating valve assembly (for turbocharger control).

      Click here

      Result
      Proceed to
      NEXT

    NEXT

    GO TO STEP 27 Click here

  26. REPAIR OR REPLACE VACUUM HOSE


    1. Repair or replace the vacuum hose.

      Result
      Proceed to
      NEXT

    NEXT

  27. CONFIRM WHETHER MALFUNCTION HAS BEEN SUCCESSFULLY REPAIRED


    1. Connect the GTS to the DLC3.

    2. Turn the ignition switch to ON.

    3. Turn the GTS ON.

    4. Clear the DTCs.


      Powertrain > Engine > Clear DTCs

    5. Turn the ignition switch off and wait for 30 seconds or more.

    6. Start the engine and warm it up.

    7. Turn the GTS ON.

    8. Read the value of Engine Speed from the Freeze Frame Data recorded previously.

      Tech Tips

      When performing the DTC detection drive pattern, make sure the engine speed increases to 2400 rpm or more and exceeds the "Engine Speed" value from the freeze frame data.

    9. After warming up the engine, drive the vehicle at a constant vehicle speed at an engine speed of 2400 rpm or more for 2 minutes [A].

    10. With the engine warmed up, fully depress the accelerator pedal for 5 seconds or more so that the engine speed is 2400 rpm or more [B].

    11. Confirm that the DTC is not output again.

      Tech Tips

      Perform the following procedure using the GTS to determine whether or not the DTC judgment has been carried out.


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


        Powertrain > Engine > Utility
        Tester Display
        All Readiness

      2. Input DTC P0234 or P1251.

      3. Check that STATUS is NORMAL.

        Tech Tips


        • If STATUS is NORMAL, DTC judgment is complete and the system is determined to be normal.

        • If STATUS is INCOMPLETE or N/A, perform [A] and [B] again.

      Result
      Proceed to
      NEXT

    NEXT

    END