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 Nitrogen Oxide emissions. The ECM monitors signals such as engine speed, 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.

The ECM opens and closes the EGR valve during fuel-cut and monitors changes in the manifold absolute pressure to detect poor movement or sticking of the EGR valve.

DTC No. DTC Detection Condition Trouble Area
P0401

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

  • Manifold absolute pressure sensor

  • ECM

Tech Tips

DTC P0401 is set while the engine is in fuel cut condition and the brake pedal is pressed for 5 seconds.

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 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).

CONFIRMATION DRIVING PATTERN

A005I4RE02

  1. Connect the intelligent tester to the DLC3.

  2. Turn the ignition switch to ON.

  3. Turn the tester on.

  4. Clear the DTCs Click here.

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

  6. Turn the ignition switch to ON and turn the tester on. [A]

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

    Tech Tips

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

  8. 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.

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

  10. Accelerate the vehicle at between 60 km/h (37 mph) then select the shift lever in 2nd gear (for M/T) or 2nd range in M (for CVT). [E]

    CAUTION:

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

  11. 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.

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

  13. 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.

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


    1. Enter the following menus: Powertrain / Engine and ECT / DTC / Pending. [G]

    2. Read the Pending DTCs.

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

      Tech Tips

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

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

  16. Input the DTC P0401.

  17. Check the DTC judgment result.

    Intelligent Tester
    Tester 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
    UNKNOWN

    • 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 malfunction.

    • If the judgment result shows INCOMPLETE or UNKNOWN and no pending DTC is output, accelerate the vehicle again at 60 km/h (37 mph) and select the 2nd gear (for M/T) or 2nd range in M (for CVT) to perform fuel cut operation for 5 seconds or more with the accelerator pedal fully released, and check the DTC judgment result.

WIRING DIAGRAM

Refer to the 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 intelligent tester. Freeze frame data records the engine conditions 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, 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 P0401)


    1. Connect the intelligent tester to the DLC3.

    2. Turn the ignition switch to ON.

    3. Turn the tester on.

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

    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 INTELLIGENT TESTER (CONTROL THE EGR STEP POSITION)


    1. Connect the intelligent tester to the DLC3.

    2. Turn the ignition switch to ON.

    3. Turn the tester on.

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

      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.

    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.

      Tech Tips


      • 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 Active Test is completed.

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

      OK
      MAP and idling condition change in response to EGR step position.
      Standard
      - 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 28 to 48 kPa

      (210 to 360 mmHg)

      (EGR valve is fully closed)

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

      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.


    NG

    REPLACE EGR VALVE ASSEMBLY Click here

    OK

  3. INSPECT EGR VALVE ASSEMBLY


    1. Remove the EGR valve assembly Click here.

    2. Check for contamination between the EGR valve and housing.

      OK
      No leaks or blockage
      Result
      Result Proceed to
      NG A
      OK B

    3. Reinstall the EGR valve assembly Click here.


    B

    CHECK FOR DEPOSIT (EXHAUST MANIFOLD CONVERTER TO EGR VALVE) Click here

    A

  4. REPLACE EGR VALVE ASSEMBLY


    1. Replace the EGR valve assembly Click here.


    NEXT

  5. CHECK FOR DEPOSIT (EXHAUST MANIFOLD CONVERTER TO EGR VALVE)


    1. Check for cracks, damage, and clogs in the pipes between the exhaust manifold converter and the EGR valve assembly.

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

      Tech Tips

      This check may require the removal of components.

      OK
      No deposits

    NG

    REPAIR OR REPLACE MALFUNCTIONING PARTS, COMPONENTS AND AREAS

    OK

  6. CHECK FOR DEPOSIT (EGR VALVE TO INTAKE PORT)


    1. Check for cracks, damage, and clogs in the pipes between the exhaust manifold converter and the EGR valve assembly.

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

      Tech Tips

      This check may require the removal of components.

      OK
      No deposits

    NG

    REPAIR OR REPLACE MALFUNCTIONING PARTS, COMPONENTS AND AREAS

    OK

  7. READ VALUE USING INTELLIGENT TESTER (MANIFOLD ABSOLUTE PRESSURE SENSOR)


    1. Connect the intelligent tester to the DLC3.

    2. Turn the ignition switch to ON.

    3. Turn the tester on.

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

    5. Read the MAP value.

      Standard
      Engine condition Tester Display
      Ignition switch ON 80 to 110 kPa (600 to 825 mmHg)

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

    7. Enter the following menus: Powertrain / Engine and ECT / Data List / Throttle Idle Position and MAP.

    8. Confirm the Throttle Idle Position is ON and check the engine idling condition and MAP when idling the engine with the A/C switch and all accessory switches should be off and shift lever in P, N or neutral.

      Standard
      Engine condition Tester Display
      Idling 28 to 48 kPa (210 to 360 mmHg)
      Result
      Result Proceed to
      NG A
      OK B

    B

    CONFIRM WHETHER MALFUNCTION HAS BEEN SUCCESSFULLY REPAIRED Click here

    A

  8. CHECK INTAKE SYSTEM


    1. Check the intake system for vacuum leaks Click here.

      OK
      No leaks in intake system.

    NG

    REPAIR OR REPLACE INTAKE SYSTEM

    OK

  9. REPLACE MANIFOLD ABSOLUTE PRESSURE SENSOR


    1. Replace the manifold absolute pressure sensor Click here.


    NEXT

  10. CONFIRM WHETHER MALFUNCTION HAS BEEN SUCCESSFULLY REPAIRED


    1. Perform the confirmation driving pattern.

      Tech Tips

      Refer to the Confirmation Driving Pattern.


    NEXT

    END