SFI SYSTEM(w/ EGR 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 stepper motor.

DTC No.

Detection Item

DTC Detection Condition

Trouble Area

Warning Indicate

Memory

P0401

Exhaust Gas Recirculation Flow Insufficient Detected

Change in the intake manifold pressure is small when the EGR valve is opened and closed during the idle fuel cut operation (2 trip detection logic).

  • EGR valve assembly

  • EGR passages

  • EGR cooler assembly

  • Manifold absolute pressure sensor

  • Intake system

Comes on

DTC stored

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

1050 to 1800 rpm

Vehicle speed

20 km/h (12.5 mph) or more

Intake air temperature

-10°C (14°F) or higher

TYPICAL MALFUNCTION THRESHOLDS

Manifold pressure change

Less than 1.8125 kPa (14 mmHg)

Engine speed

1400 rpm

CONFIRMATION DRIVING PATTERN

A232058E04

  1. Connect the intelligent tester to the DLC3.

  2. Turn the engine switch on (IG) and turn the tester on.

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

    Click here

  4. Turn the engine switch off and wait for 30 seconds.

  5. Turn the engine switch on (IG) and turn the tester on [A].

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

    Tip:

    The A/C switch and all accessory switches should be off and the shift lever should be in P or N.

  7. 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.

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

  9. Drive the vehicle at 60 km/h (37 mph) and shift the transmission to 2nd gear [E].

    CAUTION:

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

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

    Tip:

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

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

  12. Read the pending DTCs.

    Tip:

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

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

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

  14. Input the DTC: P0401.

  15. Check the DTC judgment result.

    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

    N/A

    • Unable to perform DTC judgment

    • Number of DTCs which do not fulfill DTC preconditions has reached ECU memory limit
    Tip:

    • 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 and no pending DTC is output, drive the vehicle again at 60 km/h (37 mph) and shift the transmission to 2nd gear, perform fuel cut operation for 5 seconds or more with the accelerator pedal fully released, and then check the DTC judgment result.

WIRING DIAGRAM

Figure 1. w/o Air Pump Heater
A231464E04
Figure 2. w/ Air Pump Heater
A351198E02

CAUTION / NOTICE / HINT

Tip:

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

  • When the engine is idling steadily with the EGR valve fully closed, if the EGR valve is normal and it is opened using the Active Test, the Data List values will change as follows.

    Data List

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

    Engine Speed

    Idle becomes rough

    MAP

    Pressure rises

  • Read freeze frame data using the intelligent tester. 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 FOR ANY OTHER DTCS OUTPUT (IN ADDITION TO P0401)

    1. Connect the intelligent tester to the DLC3.

    2. Turn the engine switch on (IG).

    3. Turn the tester on.

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

    5. Read DTCs.

      Powertrain > Engine and ECT > Trouble Codes

      Result

      Result

      Proceed to

      DTC P0401 is output

      A

      DTC P0401 and other DTCs are output

      B
      Tip:

      If any DTCs other than P0401 are output, perform troubleshooting for those DTCs first.

    B

    GO TO DTC CHART

    Click here

    A

  2. PERFORM ACTIVE TEST USING INTELLIGENT TESTER (OPERATE EGR VALVE)

    1. Connect the intelligent tester to the DLC3.

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

      Tip:

      • When performing the Active Test, make sure the shift lever is in P or N.

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

    3. Turn the tester on.

    4. Enter the following menus: Powertrain / Engine and ECT / Active Test / Control the EGR Step Position.

      Powertrain > Engine and ECT > Active Test

      Tester Display

      Control the EGR Step Position

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

      Tip:

      • 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.

      OK

      MAP and idling condition change in response to EGR step position as follows.

      Standard

      -

      EGR Step Position (Active Test)

      Step 0

      Step 0 to 30

      Idling condition

      Steady idling

      Idling changes from steady to rough idling or engine stalls

      MAP

      (Data List)

      -

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

      Result

      Result

      OK

      NG
    NG

    REPLACE EGR VALVE ASSEMBLYClick here

    OK

  3. INSPECT EGR VALVE ASSEMBLY

    1. Confirm that there are no deposits on the EGR valve.

    2. Confirm that the EGR valve is closed.

      OK

      There are no deposits and the valve is closed.

      Result

      Result

      OK

      NG
    OK

    CHECK FOR DEPOSIT (EGR VALVE ASSEMBLY TO INTAKE PORT)Click here

    NG

  4. REPLACE EGR VALVE ASSEMBLY

    1. Replace the EGR valve assembly.

      Click here

      Result

      Result

      NEXT
    NEXT

  5. CHECK FOR DEPOSIT (EGR VALVE ASSEMBLY TO INTAKE PORT)

    1. A217946

      Check for exhaust leaks at each connection point.

    2. Check for cracks, damage and blockage of the pipes between the intake manifold converter and EGR valve assembly.

      Tip:

      This check may require the removal of components.

    3. Check for blockage due to deposits in the EGR valve and pipes.

      OK

      No deposits.

      Result

      Result

      OK

      NG
    NG

    REPAIR OR REPLACE MALFUNCTIONING PARTS

    OK

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

    1. Check for exhaust leaks at each connection point.

      A280872

    2. Check for cracks, damage and blockage of the pipes between the exhaust manifold converter and EGR valve assembly.

      Tip:

      This check may require the removal of components.

    3. Check for blockage due to deposits in the EGR valve and pipes.

      OK

      No deposits.

      Result

      Result

      OK

      NG
    NG

    REPAIR OR REPLACE MALFUNCTIONING PARTS

    OK

  7. INSPECT EGR COOLER ASSEMBLY

    1. Check for blockage in the EGR cooler assembly.

      Result

      Result

      OK

      NG
    NG

    REPAIR OR REPLACE EGR COOLER ASSEMBLY

    Click here

    OK

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

    1. Connect the intelligent tester to the DLC3.

    2. Turn the engine switch on (IG).

    3. Turn the tester on.

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

      Powertrain > Engine and ECT > Data List

      Tester Display

      MAP

    5. Read the MAP value.

      Standard

      Switch Condition

      Tester Display

      Engine switch on (IG)

      80 to 110 kPa (600 to 825 mmHg)

      Result

      Result

      OK

      NG
    OK

    CONFIRM WHETHER MALFUNCTION HAS BEEN SUCCESSFULLY REPAIREDClick here

    NG

  9. CHECK INTAKE SYSTEM

    1. Check the intake system for vacuum leaks.

      Click here

      OK

      No leaks in intake system.

      Result

      Result

      OK

      NG
    NG

    REPAIR OR REPLACE INTAKE SYSTEM

    Click here

    OK

  10. REPLACE MANIFOLD ABSOLUTE PRESSURE SENSOR

    1. Replace the manifold absolute pressure sensor.

      Click here

      Result

      Result

      NEXT
    NEXT

  11. CONFIRM WHETHER MALFUNCTION HAS BEEN SUCCESSFULLY REPAIRED

    1. Connect the intelligent tester to the DLC3.

    2. Turn the engine switch on (IG).

    3. Turn the tester on.

    4. Clear the DTCs.

      Click here

      Powertrain > Engine and ECT > Clear DTCs

    5. Turn the engine switch off and wait for 30 seconds.

    6. Turn the engine switch on (IG) and turn the tester on.

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

      Tip:

      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.

    9. Idle the engine for 30 seconds or more.

    10. Drive the vehicle at 60 km/h (37 mph).

      CAUTION:

      Strictly observe speed limits and traffic laws when performing the confirmation drive pattern.

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

      Tip:

      If the deceleration was not completed, perform the Confirmation Driving Pattern again.

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

    13. Read the pending DTCs.

      Powertrain > Engine and ECT > Trouble Codes

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

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

      Powertrain > Engine and ECT > Utility

      Tester Display

      All Readiness

    16. Input the DTC: P0401.

    17. Check the DTC judgment result.

      Result

      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

      N/A

      • Unable to perform DTC judgment

      • Number of DTCs which do not fulfill DTC preconditions has reached ECU memory limit

      Result

      Result

      NEXT
    NEXT

    END