SFI SYSTEM, Diagnostic DTC:P0401

DTC Code DTC Name
P0401 Exhaust Gas Recirculation Flow Insufficient Detected

DESCRIPTION

Based on the driving conditions, the ECM regulates the volume of exhaust gas that is recirculated to the engine's combustion chambers and thus lowers the combustion temperature to reduce NOx emissions. The ECM monitors signals such as engine speed, engine coolant temperature, electric load, and vehicle speed. When the EGR permission conditions are fulfilled, the ECM controls the opening of the EGR valve linearly through signals to the EGR step motor.

DTC No. Detection Item DTC Detection Condition Trouble Area MIL Memory
P0401 Exhaust Gas Recirculation Flow Insufficient Detected

Change in intake manifold pressure is small when the EGR valve opened and closed during fuel cut operation

(2 trip detection logic).

  • EGR valve assembly

  • EGR passage

  • Vacuum sensor (manifold absolute pressure sensor)

  • ECM

 Comes on (Euro-OBD) / - (Except Euro-OBD) DTC stored (Euro-OBD) / - (Except Euro-OBD)

MONITOR DESCRIPTION

The ECM monitors the pressure inside the intake manifold while opening and closing the EGR valve during fuel cut operation. If there is no change in the vacuum sensor (manifold absolute pressure sensor) value, the ECM interprets this as a malfunction in the EGR valve assembly, illuminates the MIL and stores the DTC (2 trip detection logic).

MONITOR STRATEGY

Required Sensors/Components (Main)

EGR valve assembly

Vacuum sensor (manifold absolute pressure sensor)
Required Sensors/Components (Related)

Engine coolant temperature sensor

Vehicle speed sensor
Frequency of Operation Continuous

CONFIRMATION DRIVING PATTERN

A00471AE09

  1. Connect the GTS to the DLC3.

  2. Turn the ignition switch to ON.

  3. Turn the GTS on.

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

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

  6. Turn the ignition switch to ON [A].

  7. Turn the GTS on.

  8. Start the engine and warm it up until the engine coolant temperature reaches 75°C (167°F) or higher [B].

    Tech Tips

    The A/C switch and all accessory switches should be off.

  9. Drive the vehicle at 60 km/h (37 mph) for 5 minutes or more [C].

    CAUTION:

    When performing the confirmation driving pattern, obey all speed limits and traffic laws.

  10. Idle the engine for 30 seconds or more [D].

  11. Accelerate the vehicle to 60 km/h (37 mph) [E].

    CAUTION:

    When performing the confirmation driving pattern, obey all speed limits and traffic laws.

  12. Perform the fuel cut operation for 5 seconds or more, with the accelerator pedal fully released [F].

    Tech Tips

    When the fuel cut is operating, "Idle Fuel Cut" in Data List is ON.

  13. Enter the following menus: Powertrain / Engine and ECT / Data List / EGR/VVT Monitor.

  14. Check that the item EGR/VVT Monitor displays is Compl (Complete) or Incmpl (Incomplete).

    Tech Tips

    If the EGR/VVT Monitor is Incmpl (Incomplete), perform the driving pattern again.

  15. If the EGR/VVT Monitor is still Incmpl (Incomplete), perform the following procedure.

    (a) Enter the following menus: Powertrain / Engine and ECT / Trouble Codes [G].

    (b) Read the pending DTCs.

    Tech Tips


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

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

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

  17. Input the DTC P0401.

  18. 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 memory limit

    Tech Tips


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

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

    • If the judgment result shows INCOMPLETE or N/A, perform the Confirmation Driving Pattern and the DTC judgment result again.

WIRING DIAGRAM

Refer to DTC P0403.

Click here

CAUTION / NOTICE / HINT

Tech Tips


  • By using the Control the EGR Step Position Active Test, the operation of the EGR valve can be checked.

  • If the EGR valve is normal, the engine condition is as follows:

    The engine idles steady while the EGR valve is fully closed. When the EGR valve is opened using the Active Test, the Data List values will change as shown in the table below.

    Data List Change
    Engine Speed Idle becomes rough
    MAP Pressure rises

  • 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 help determine if the vehicle was moving or stationary, if the engine was warmed up or not, if the air fuel ratio was lean or rich, and other data from the time the malfunction occurred.

PROCEDURE


  1. CHECK ANY OTHER DTCS OUTPUT (IN ADDITION TO DTC P0401)


    1. Connect the GTS to the DLC3.

    2. Turn the ignition switch to ON.

    3. Turn the GTS on.

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

    5. Read the DTC.

      Result
      Result Proceed to
      DTC P0401 is output A
      DTC P0401 and other DTCs are output B

      Tech Tips

      If any DTCs other than P0401 are output, troubleshoot those DTCs first.


    B

    GO TO DTC CHART Click here

    A

  2. PERFORM ACTIVE TEST USING GTS (CONTROL THE EGR STEP POSITION)


    1. Connect the GTS to the DLC3.

    2. Turn the ignition switch to ON.

    3. Turn the GTS on.

    4. Start the engine and warm it up until the engine coolant temperature reaches 75°C (167°F) or higher.

      Tech Tips

      The A/C switch and all accessory switches should be off.

    5. Enter the following menus: Powertrain / Engine and ECT / Active Test / Control the EGR Step Position / Data List / MAP and Throttle Idle Position.

    6. Confirm that the Throttle Idle Position is ON and check the engine idling condition and MAP values in the Data List while performing the Active Test.

      OK
      MAP and idling condition change in response to EGR step position.
      - EGR Step Position (Active Test)
      0 Steps 0 to 30 Steps
      Idling condition Steady idling Idling changes from steady to rough idling or engine stalls

      MAP

      (Data List)

      MAP value is 20 to 48 kPa(abs)

      [150 to 360 mmHg(abs)]

      (EGR valve is fully closed)

      		 MAP value is at least +10 kPa (75 mmHg) higher than when EGR valve is fully closed

      Note


      • Do not leave the EGR valve open for 10 seconds or more during the Active Test.

      • Be sure to return the EGR valve to step 0 when the Active Test is completed.

      • Do not open the EGR valve 30 steps or more during the Active Test.

      Tech Tips

      During Active Test, if the idling condition does not change in response to EGR step position, then there is probably a malfunction in the EGR valve assembly.

      Result
      Proceed to
      OK
      NG

    NG

    GO TO STEP 4 Click here

    OK

  3. INSPECT EGR VALVE ASSEMBLY


    1. Remove the EGR valve assembly.

      Click here

    2. Check if the EGR valve is stuck open.

      OK
      EGR valve is tightly closed.
      Result
      Result Proceed to
      NG A
      OK B

    B

    GO TO STEP 5 Click here

    A

  4. REPLACE EGR VALVE ASSEMBLY


    1. Replace the EGR valve assembly.

      Click here

      Tech Tips

      Perform "Inspection After Repair" after replacing the EGR valve assembly.

      Click here

      Result
      Proceed to
      NEXT

    NEXT

  5. CHECK FOR DEPOSIT (EXHAUST MANIFOLD CONVERTER SUB-ASSEMBLY AND INTAKE PORT TO EGR VALVE ASSEMBLY)

    A0048RE

    1. Check for exhaust gas leaks at each connection point.

    2. Check for cracks, damage, and clogs in the pipes between the exhaust manifold converter sub-assembly, the intake manifold and the EGR valve assembly.

    3. Check if there is a built-up of deposits in the EGR valve of pipes.

      Tech Tips

      This check may require the removal of components.

      OK
      No deposits

      Tech Tips

      Perform "Inspection After Repair" after repairing or replacing the exhaust system.

      Click here

      Result
      Proceed to
      OK
      NG

    NG

    REPAIR OR REPLACE MALFUNCTIONING PARTS, COMPONENTS AND AREAS

    OK

  6. READ VALUE USING GTS (MAP)


    1. Connect the GTS to the DLC3.

    2. Turn the ignition switch to ON.

    3. Turn the GTS on.

    4. Enter the following menus: Powertrain / Engine and ECT / Data List / MAP.

    5. Read the MAP value.

      Standard
      Engine condition GTS Display
      Ignition switch ON 80 to 110 kPa(abs) [600 to 825 mmHg(abs)]
      Result
      Proceed to
      OK
      NG

    OK

    GO TO STEP 9 Click here

    NG

  7. CHECK INTAKE SYSTEM


    1. Check the intake system for vacuum leaks.

      Click here

      OK
      No leaks in intake system.

      Tech Tips

      Perform "Inspection After Repair" after repairing or replacing the intake system.

      Click here

      Result
      Proceed to
      OK
      NG

    NG

    REPAIR OR REPLACE INTAKE SYSTEM

    OK

  8. REPLACE VACUUM SENSOR (MANIFOLD ABSOLUTE PRESSURE SENSOR)


    1. Replace the vacuum sensor (manifold absolute pressure sensor).

      Click here

      Result
      Proceed to
      NEXT

    NEXT

  9. 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.

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

    6. Turn the ignition switch to ON.

    7. Turn the GTS on.

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

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

    10. Input the DTC: P0401.

    11. Check the DTC judgment result.

      Result
      Result Proceed to

      NORMAL

      (DTC P0401 is output)

      		 A

      ABNORMAL

      (DTCs are not output)

      		 B

    A

    END

    B

    REPLACE ECM Click here