SFI SYSTEM, Diagnostic DTC:P0401

DTC Code DTC Name
P0401 Exhaust Gas Recirculation Flow Insufficient Detected

DESCRIPTION

The ECM lowers combustion chamber temperatures and reduces Nitrogen Oxide (Nox) emissions by recirculating an appropriate amount of exhaust gas to the combustion chambers according to the engine operating conditions. When all EGR activation conditions are met (based on sensor signals such as engine speed, coolant temperature, load signal, vehicle speed signal), the ECM turns on the stepper motor inside the EGR valve and linearly controls the opening angle of the EGR valve. The EGR gas temperature sensor detects the EGR gas temperature in the EGR valve and sends a signal to the ECM to confirm EGR valve operation. The ECM also sets a DTC if the difference between the coolant temperature and the EGR gas temperature exceeds the threshold value during EGR operation.

DTC No. DTC Detection Condition Trouble Area
P0401

When engine started and EGR valve operation beginning, EGR gas temperature value is less than the threshold value for 5 seconds.

(2 trip detection logic)

  • Open or short in EGR valve assembly circuit

  • EGR valve assembly

  • Open or short in EGR gas temperature sensor circuit

  • EGR gas temperature sensor

  • ECM

WIRING DIAGRAM

Refer to the DTC P0403 Click here.

CAUTION / NOTICE / HINT

Note

Inspect the fuses for circuits related to this system before performing the following inspection procedure.

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.

  • Read freeze frame data using the intelligent tester. 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, if the air-fuel ratio was lean or rich, and other data from the time the malfunction occurred.

PROCEDURE


  1. READ VALUE USING INTELLIGENT TESTER (EGR GAS TEMPERATURE)


    1. Connect the intelligent tester to the DLC3.

    2. Turn the ignition switch to the ON position and tester on.

    3. Select the following menu items: Powertrain / Engine and ECT / Data List / EGR Gas Temperature.

    4. Read the values displayed on the tester.

      Result
      Result Proceed to
      3 to 158°C (37.4 to 316.4°F) A
      Less than 3°C (37.4°F) B
      158°C (316.4°F) or more B

    B

    INSPECT EGR GAS TEMPERATURE SENSOR Click here

    A

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


    1. Connect the intelligent tester to the DLC3.

    2. Start the engine and tester on.

    3. Select the following menu items: Powertrain / Engine and ECT / Active Test / Control the EGR Position / EGR Position.

      Standard
      EGR Position Specified Condition
      0% Normal engine speed
      100% Engine idles roughly or stalls

    NG

    INSPECT EGR VALVE ASSEMBLY Click here

    OK

  3. INSPECT EGR GAS TEMPERATURE SENSOR


    1. Inspect the EGR gas temperature sensor Click here.


    NG

    REPLACE EGR GAS TEMPERATURE SENSOR Click here

    OK

  4. CHECK HARNESS AND CONNECTOR (ECM - EGR GAS TEMPERATURE SENSOR)


    1. Disconnect the ECM connector.

    2. Disconnect the EGR gas temperature sensor connector.

    3. Measure the resistance according to the value(s) in the table below.

      Standard resistance (Check for open)
      Tester Connection Condition Specified Condition
      B52-2 - B23-87 (THG) Always Below 1 Ω
      B52-1 - B23-119 (ETHG) Always Below 1 Ω
      Standard resistance (Check for short)
      Tester Connection Condition Specified Condition
      B52-2 or B23-87 (THG) - Body ground Always 10 kΩ or higher
      B52-1 or B23-119 (ETHG) - Body ground Always 10 kΩ or higher

    4. Reconnect the ECM connector.

    5. Reconnect the EGR gas temperature sensor connector.


    OK

    REPLACE ECM Click here

    NG

    REPAIR OR REPLACE HARNESS OR CONNECTOR (ECM - EGR GAS TEMPERATURE SENSOR)

  5. INSPECT EGR VALVE ASSEMBLY


    1. Inspect the EGR valve assembly Click here.


    NG

    REPLACE EGR VALVE ASSEMBLY Click here

    OK

  6. CHECK HARNESS AND CONNECTOR (EGR VALVE POWER SOURCE CIRCUIT)


    1. A005HYYE01
      Text in Illustration
      *a

      Front view of wire harness connector

      (to EGR Valve Assembly)

      Disconnect the EGR valve connector.

    2. Turn the ignition switch to ON.

    3. Measure the voltage according to the value(s) in the table below.

      Standard voltage
      Tester Connection Condition Specified Condition
      B56-2 (+B1) - Body ground Ignition switch ON 11 to 14 V
      B56-5 (+B2) - Body ground Ignition switch ON 11 to 14 V

    4. Reconnect the EGR valve connector.


    NG

    CHECK HARNESS AND CONNECTOR (EGR VALVE ASSEMBLY - NO. 1 INTEGRATION RELAY) Click here

    OK

  7. CHECK HARNESS AND CONNECTOR (ECM - EGR VALVE)


    1. Disconnect the ECM connector.

    2. Disconnect the EGR valve connector.

    3. Measure the resistance according to the value(s) in the table below.

      Standard resistance (Check for open)
      Tester Connection Condition Specified Condition
      B56-4 (EGR1) - B23-28 (EGR1) Always Below 1 Ω
      B56-3 (EGR2) - B23-27 (EGR2) Always Below 1 Ω
      B56-6 (EGR3) - B23-26 (EGR3) Always Below 1 Ω
      B56-1 (EGR4) - B23-25 (EGR4) Always Below 1 Ω
      Standard resistance (Check for short)
      Tester Connection Condition Specified Condition
      B56-4 (EGR1) or B23-28 (EGR1) - Body ground Always 10 kΩ or higher
      B56-3 (EGR2) or B23-27 (EGR2) - Body ground Always 10 kΩ or higher
      B56-6 (EGR3) or B23-26 (EGR3) - Body ground Always 10 kΩ or higher
      B56-1 (EGR4) or B23-25 (EGR4)- Body ground Always 10 kΩ or higher

    4. Reconnect the ECM connector.

    5. Reconnect the EGR valve connector.


    NG

    REPAIR OR REPLACE HARNESS OR CONNECTOR (ECM - EGR VALVE)

    OK

  8. INSPECT EGR PIPE


    1. Check the EGR pipe for leaks or blockage.

      OK
      No leaks or blockage

    NG

    REPAIR OR REPLACE EGR PIPE

    OK

  9. INSPECT EGR VALVE (VISUALLY CHECK THROTTLE VALVE)


    1. Remove the EGR valve Click here.

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

      OK
      EGR valve is not contaminated with foreign objects.

    3. Reinstall the EGR valve Click here.


    OK

    REPLACE ECM Click here

    NG

    REPLACE EGR VALVE Click here

  10. CHECK HARNESS AND CONNECTOR (EGR VALVE ASSEMBLY - NO. 1 INTEGRATION RELAY)


    1. Disconnect the EGR valve connector.

    2. Remove the No. 1 integration relay from the engine room main relay block.

    3. Measure the resistance according to the value(s) in the table below.

      Standard resistance (Check for open)
      Tester Connection Condition Specified Condition
      B56-2 (+B1) - 1E-4 Always Below 1 Ω
      B56-5 (+B2) - 1E-4 Always Below 1 Ω
      Standard resistance (Check for short)
      Tester Connection Condition Specified Condition
      B56-2 (+B1) or 1E-4 - Body ground Always 10 kΩ or higher
      B56-5 (+B2) or 1E-4 - Body ground Always 10 kΩ or higher

    4. Reconnect the EGR valve connector.

    5. Reinstall the No. 1 integration relay.


    OK

    CHECK ECM POWER SOURCE CIRCUIT Click here

    NG

    REPAIR OR REPLACE HARNESS OR CONNECTOR (EGR VALVE ASSEMBLY - NO. 1 INTEGRATION RELAY)