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, 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. DTC Detection Condition Trouble Area
P0401

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

(2 trip detection logic).

  • EGR valve assembly

  • EGR passage

  • EGR cooler assembly

  • Manifold absolute pressure sensor

  • Intake system

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).

MONITOR STRATEGY

Required Sensors/Components (Main)

EGR valve assembly

Manifold absolute pressure sensor
Required Sensors/Components (Related)

Engine coolant temperature sensor

Vehicle speed sensor
Frequency of Operation Once per driving cycle

TYPICAL ENABLING CONDITIONS

Engine speed 950 to 1600 rpm
Vehicle speed 20 km/h (12.4 mph) or more
Intake air temperature -10°C (14°F) or higher

TYPICAL MALFUNCTION THRESHOLDS

Manifold pressure change Less than 1.75 kPa(gauge) [13.1 mmHg(gauge)]
At engine speed 1050 rpm

CONFIRMATION DRIVING PATTERN

A004FUAE24

  1. Connect the GTS to the DLC3.

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

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

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

  5. Turn the ignition switch to ON (IG) and turn the GTS on.

  6. Put the engine in inspection mode (maintenance mode) Click here.

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

  8. Accelerate the vehicle to 75 km/h (47 mph) or more by depressing the accelerator pedal for at least 10 seconds [B].

    CAUTION:

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

    Tech Tips

    When accelerating the vehicle, depress the accelerator pedal more than normal to start the engine.

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

  10. Accelerate the vehicle to 75 km/h (47 mph) with the shift lever in B [D].

    CAUTION:

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

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

    Tech Tips

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

  12. Enter the following menus: Powertrain / Engine and ECT / Trouble Codes [F].

  13. Read the pending DTCs.

    Tech Tips


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

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

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

  15. Input the DTC: P0401.

  16. 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 DTC judgment result is INCOMPLETE or N/A, perform steps [D] and [F] again.

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 and is opened using the Active Test, the Data List value changes as follows.

    Data List Change in Data List when Number of Steps is Increased Using Control the EGR Step Position Active Test
    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 (IG).

    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 power switch on (IG).

    3. Turn the GTS on.

    4. Put the engine in inspection mode (maintenance mode) Click here.

    5. 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.

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

    7. Confirm that the Throttle Idle Position is ON and check the MAP value in the Data List while performing the Active Test.

      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.

      OK
      MAP change in response to EGR step position when Throttle Idle Position is ON in Data List.
      Standard
      - EGR Step Position (Active Test)
      0 Steps 0 to 30 Steps

      MAP

      (Data List)

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

      Tech Tips


      • While performing the Active Test, if the increase in the value of MAP is small, the EGR valve assembly may be a malfunctioning.

      • Even if the EGR valve assembly is malfunctioning, rough idling or an increase in the value of MAP may occur while performing the Active Test. However, the amount that the value of MAP increases will be smaller than normal.


    NG

    REPLACE EGR VALVE ASSEMBLY Click here

    OK

  3. INSPECT EGR VALVE ASSEMBLY


    1. Check if the EGR valve are clogged with deposits.

    2. Check if the EGR valve is closed.

      OK
      EGR valve is closed and no deposits.
      Result
      Result Proceed to
      NG A
      OK B

    B

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


    NEXT

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

    A004E8F

    1. Check for exhaust leaks at each connection point.

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

    3. This check may require the removal of components.

    4. Check if there is a build-up of deposits in the EGR valve of pipes.

      OK
      No deposits.

      Tech Tips

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


    NG

    REPAIR OR REPLACE MALFUNCTIONING PARTS, COMPONENT AND AREA

    OK

  6. INSPECT EGR COOLER ASSEMBLY


    1. Check for blockage of the EGR cooler assembly.


    NG

    REPLACE EGR COOLER ASSEMBLY Click here

    OK

  7. READ VALUE USING GTS (MAP)


    1. Connect the GTS to the DLC3.

    2. Turn the ignition switch to ON (IG).

    3. Turn the GTS on.

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

    5. Read the MAP value.

      Standard
      Condition GTS Display
      Ignition switch ON (IG) 80 to 110 kPa(abs) [600 to 825 mmHg(abs)]

      Tech Tips

      Standard atmospheric pressure is 101 kPa(abs) [758 mmHg]. For every 100 m (328 ft) increase in altitude, pressure drops by 1 kPa (7.5 mmHg). The pressure also varies due to the weather (high atmospheric pressure, low atmospheric pressure).

    6. Put the engine in inspection mode (maintenance mode) Click here.

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

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

    9. Read the MAP value when idling the engine with the A/C switch and all accessory switches should be off and shift lever in P or N.

      Standard
      Engine Condition GTS Display
      Idling 20 to 40 kPa(abs) [150 to 300 mmHg(abs)]
      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.

      Tech Tips

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


    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. Connect the GTS to the DLC3.

    2. Turn the ignition switch to ON (IG).

    3. Turn the GTS 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 (IG).

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

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

    9. Read the pending DTCs.

      Tech Tips


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

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

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

    11. Input the DTC: P0401.

    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 memory limit

    NEXT

    END