ECD SYSTEM, Diagnostic DTC:P0401

DTC Code DTC Name
P0401 Exhaust Gas Recirculation "A" Flow Insufficient Detected

DESCRIPTION

Depending on the operating condition, a certain quantity of exhaust gas is recirculated via the EGR valve assembly into the intake area.

This reduces nitrogen oxide emissions.

The exhaust-gas recirculation control is only active at low engine speeds and loads.

Tech Tips

For more information on the EGR control, refer to System Description Click here.

DTC No. DTC Detection Condition Trouble Area
P0401

During normal operation, EGR negative deviation falls below limit value, or EGR rate exceeds limit value for 5 seconds or more

(3 trip detection logic)

  • Intake system air leak

  • Exhaust system exhaust gas leak

  • Diesel throttle body assembly

  • EGR valve assembly

  • Turbocharger sub-assembly

  • EGR cooler assembly

  • ECM

INSPECTION PROCEDURE

Note


  • When replacing the ECM, the ECM needs Registration and Initialization Click here.

  • After replacing the EGR valve assembly, the ECM needs initialization Click here.

  • After replacing the mass air flow meter, the ECM needs initialization Click here.

Tech Tips


  • When the ECM must be replaced, before replacing the ECM, perform the "Learning Values Save" function using the GTS. Then after installing the new ECM, perform all of the initialization/registrations for the "Learning Values Write" function by following the instructions shown on the GTS display.

  • Read freeze frame data using the GTS. Freeze frame data records the engine condition when malfunctions are detected. When troubleshooting, freeze frame data can help determine if the vehicle was moving or stationary, if the engine was warmed up or not, and other data from the time the malfunction occurred.

PROCEDURE


  1. CHECK INTAKE SYSTEM


    1. Check for air leaks in the intake system after the turbocharger sub-assembly.

      OK
      No leakage.

    NG

    REPAIR OR REPLACE INTAKE SYSTEM Click here

    OK

  2. CHECK MASS AIR FLOW METER


    1. Check for DTCs related to the validity of the mass air flow meter.


    OK

    CHECK DIESEL THROTTLE BODY ASSEMBLY Click here

    NG

    CHECK EXHAUST SYSTEM Click here

  3. CHECK EXHAUST SYSTEM


    1. Check for exhaust gas leaks in the exhaust system before the turbocharger sub-assembly.

      OK
      No leakage.

    NG

    REPAIR OR REPLACE EXHAUST SYSTEM Click here

    OK

  4. CHECK DIESEL THROTTLE BODY ASSEMBLY


    1. Check for DTCs related to the diesel throttle body assembly.

      OK
      DTCs related to the diesel throttle body assembly are not output.

    NG

    REPAIR OR REPLACE DIESEL THROTTLE BODY ASSEMBLY Click here

    OK

  5. CHECK EGR VALVE ASSEMBLY


    1. Check for DTCs related to the EGR valve assembly.

      OK
      DTCs related to the EGR valve assembly are not output.

    NG

    REPAIR OR REPLACE EGR VALVE ASSEMBLY Click here

    OK

  6. CHECK TURBOCHARGER SUB-ASSEMBLY


    1. Check for DTCs related to the turbocharger sub-assembly.

      OK
      DTCs related to the turbocharger sub-assembly are not output.

    NG

    REPAIR OR REPLACE TURBOCHARGER SUB-ASSEMBLY Click here

    OK

  7. CHECK EGR COOLER ASSEMBLY


    1. Check that the airflow is not slowed by soot deposits in the EGR cooler.

      OK
      Airflow is not slowed by soot deposits.

    NG

    CLEAN OR REPLACE EGR COOLER ASSEMBLY Click here

    OK

  8. CHECK WHETHER DTC OUTPUT RECURS (DTC P0401)


    1. Connect the GTS to the DLC3.

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

    3. Clear the DTCs Click here.

    4. Turn the ignition switch off and wait for 60 seconds or more [A].

    5. Perform road test [B].

    6. Repeat [A] and [B] for the number of trips detected.

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

    8. Read the DTCs.

      Result
      Result Proceed to
      No DTC output A
      DTC P0401 B

    B

    REPLACE ECM Click here

    A

    END

  9. REPAIR OR REPLACE INTAKE SYSTEM


    1. Repair or replace the malfunctioning parts of the intake system.


    NEXT

    CONFIRM WHETHER MALFUNCTION HAS BEEN SUCCESSFULLY REPAIRED Click here

  10. REPAIR OR REPLACE EXHAUST SYSTEM


    1. Repair or replace the malfunctioning parts of the exhaust system.


    NEXT

    CONFIRM WHETHER MALFUNCTION HAS BEEN SUCCESSFULLY REPAIRED Click here

  11. REPAIR OR REPLACE DIESEL THROTTLE BODY ASSEMBLY


    1. Repair or replace diesel throttle body assembly or perform inspections and troubleshooting for related DTCs Click here.


    NEXT

    CONFIRM WHETHER MALFUNCTION HAS BEEN SUCCESSFULLY REPAIRED Click here

  12. REPAIR OR REPLACE EGR VALVE ASSEMBLY


    1. Repair or replace EGR valve assembly or perform inspections and troubleshooting for related DTCs Click here.


    NEXT

    CONFIRM WHETHER MALFUNCTION HAS BEEN SUCCESSFULLY REPAIRED Click here

  13. REPAIR OR REPLACE TURBOCHARGER SUB-ASSEMBLY


    1. Repair or replace turbocharger sub-assembly or perform inspections and troubleshooting for related DTCs Click here.


    NEXT

    CONFIRM WHETHER MALFUNCTION HAS BEEN SUCCESSFULLY REPAIRED Click here

  14. CLEAN OR REPLACE EGR COOLER ASSEMBLY


    1. Clean or replace the EGR cooler assembly.


    NEXT

    CONFIRM WHETHER MALFUNCTION HAS BEEN SUCCESSFULLY REPAIRED Click here

  15. REPLACE ECM


    1. Replace the ECM Click here.


    NEXT

  16. CONFIRM WHETHER MALFUNCTION HAS BEEN SUCCESSFULLY REPAIRED


    1. Connect the GTS to the DLC3.

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

    3. Clear the DTCs Click here.

    4. Turn the ignition switch off and wait for 60 seconds or more [A].

    5. Perform road test [B].

    6. Repeat [A] and [B] for the number of trips detected.

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

    8. Confirm that the DTC is not output again.


    NEXT

    END