ECD SYSTEM (for DPF), Diagnostic DTC:P0400

DTC Code DTC Name
P0400 Exhaust Gas Recirculation Flow

DESCRIPTION

The EGR system recirculates exhaust gases. The recirculated gas mingles with the intake air so that the EGR system can slow combustion speed and keep the combustion temperature down. This helps reduce NOx emissions.

In order to increase EGR circulation efficiency, the ECM adjusts the EGR valve angle and the throttle valve angle.

P0400
DTC Detection Drive Pattern DTC Detection Condition Trouble Area
After warming up the engine, decelerate from a speed of 80 km/h (50 mph) or more (fully release the accelerator pedal for approximately 5 seconds).

Mass air flow rate is not changed when turning on the electric EGR control valve assembly while decelerating.

(2 trip detection logic)

  • EGR valve deposit

  • EGR valve passage deposit

  • EGR cooler

  • Mass air flow meter
Related Data List
DTC No. Data List
P0400

  • MAF

  • Target EGR Position

  • Actual EGR Valve Pos.

MONITOR DESCRIPTION

If the EGR valve is forcibly operated during deceleration but the intake air amount does not vary, the ECM determines that the EGR valve is malfunctioning. The ECM then illuminates the MIL (2 trip detection logic).

A01DWULE03

INSPECTION PROCEDURE

Note


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

  • After replacing the ECM, the new ECM needs registration Click here and initialization Click here.

  • After replacing the fuel supply pump assembly, the ECM needs initialization Click here.

  • After replacing an injector assembly, the ECM needs registration Click here.

Tech Tips

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, and other data from the time the malfunction occurred.

PROCEDURE


  1. CHECK FOR ANY OTHER DTCS OUTPUT (IN ADDITION TO DTC P0400)


    1. Connect the intelligent tester to the DLC3.

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

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

    4. Read the DTCs.

      Result
      Result Proceed to
      P0400 is output A
      P0400 and other DTCs are output B

    B

    GO TO DTC CHART Click here

    A

  2. PERFORM ACTIVE TEST USING INTELLIGENT TESTER (ACTIVATE THE EGR VALVE CLOSE)


    1. Connect the intelligent tester to the DLC3.

    2. Start the engine and warm it up, and make sure the A/C switch and all accessory switches are off.

    3. Turn the ignition switch off. Wait for 30 seconds, and then restart the engine.

    4. Turn the tester on.

    5. Enter the following menus: Powertrain / Engine and ECT / Data List / MAF.

    6. Read the MAF value displayed on the tester while the engine is idling.

    7. Enter the following menus: Powertrain / Engine and ECT / Active Test / Activate the EGR Valve Close.

    8. Read the MAF value when the EGR valve is closed using the Active Test function.

      Tech Tips


      • If idling continues for 20 minutes or more, the EGR valve target opening angle becomes 0% (EGR valve fully closed). As this makes diagnosis impossible, it becomes necessary to drive the vehicle or to restart the engine.

      • Before performing the diagnosis, confirm that the EGR valve target opening angle is not 0%.

      • When "Coolant Temp" is 75°C (167°F) or higher during idling, the exhaust gas flows through the EGR cooler. If MAF does not change when the EGR is cut even though the EGR valve is operating normally, the EGR cooler may be clogged.

      • When idling while warming up the engine, the actuator operates and the EGR cooler is bypassed. However, if the connector of the VSV for the EGR cooler is disconnected, the EGR cooler is not bypassed and it is possible to check how clogged the EGR cooler is.

      Result
      Active Test Result Proceed to

      Activate the EGR Valve Close:

      Off (Open) to On (Closed)

      		 MAF value does not change A
      MAF value changes B

      Note

      As the measured values may differ from those shown below due to factors such as differences in measuring environments and changes in vehicle condition due to aging, do not use these values to determine whether the vehicle is malfunctioning or not.

      Tech Tips

      The problem may be a temporary one, due to the entry of deposits or foreign matter. Check that there are no deposits or foreign matter in the electric EGR control valve assembly or mass air flow meter.

      Reference
      EGR Valve Condition (Opening) Measuring Condition MAF (Reference)
      Open (55%)

      • Atmosphere pressure: 101 kPa

      • Intake air temperature: 30°C (86°F)

      • Engine coolant temperature: 88°C (190°F)

      		 3 to 10 gm/s
      Closed (0%) 12 to 21 gm/s

    B

    PERFORM ACTIVE TEST USING INTELLIGENT TESTER (ACTIVATE THE VSV FOR EGR COOLER BYPASS) Click here

    A

  3. READ VALUE USING INTELLIGENT TESTER (MAF)


    1. Connect the intelligent tester to the DLC3.

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

    3. Enter the following menus: Powertrain / Engine and ECT / Data List / MAF.

    4. With the ignition switch ON and engine stopped, read the value when 30 seconds has elapsed.

      Standard
      Tester Display Switch Condition Standard
      MAF Ignition switch ON (do not start engine) Less than 0.35 gm/s

    NG

    REPLACE MASS AIR FLOW METER Click here

    OK

  4. PERFORM ACTIVE TEST USING INTELLIGENT TESTER (ACTIVATE THE VSV FOR EGR COOLER BYPASS)


    1. Connect the intelligent tester to the DLC3.

    2. Start the engine and warm it up, and make sure the A/C switch and all accessory switches are off.

    3. Turn the ignition switch off and wait for 30 seconds.

    4. Start the engine and turn the tester on.

    5. Enter the following menus: Powertrain / Engine and ECT / Data List / MAF.

    6. Read the MAF value displayed on the tester while the engine is idling.

    7. Enter the following menus: Powertrain / Engine and ECT / Active Test / Activate the VSV for EGR Cooler Bypass / Data List / EGR Cooler Bypass Position.

      Tech Tips

      Whether the EGR is passing through the bypass side or cooler side during the Active Test can be confirmed by checking EGR Cooler Bypass Position.

    8. Using the Active Test function, switch the EGR valve bypass switching valve between "Cooler" and "Bypass" a few times, and then check whether the MAF value changes after switching the valve from "Cooler" to "Bypass".

      Tech Tips

      If idling continues for 20 minutes or more, the EGR valve target opening angle becomes 0% (EGR valve fully closed). As this makes diagnosis impossible, it becomes necessary to drive the vehicle or restart the engine.

      Result
      Tester Display Result Proceed to

      Activate the VSV for EGR Cooler Bypass:

      Cooler to Bypass

      		 MAF value does not change A
      MAF value changes B

      Tech Tips

      If the EGR cooler is clogged, the mass air flow changes.


    A

    CHECK FOR DEPOSIT (ELECTRIC EGR CONTROL VALVE ASSEMBLY) Click here

    B

    REPLACE EGR COOLER Click here

  5. PERFORM ACTIVE TEST USING INTELLIGENT TESTER (ACTIVATE THE VSV FOR EGR COOLER BYPASS)


    1. Connect the intelligent tester to the DLC3.

    2. Start the engine and warm it up, and make sure the A/C switch and all accessory switches are off.

    3. Turn the ignition switch off and wait for 30 seconds.

    4. Start the engine and turn the tester on.

    5. Enter the following menus: Powertrain / Engine and ECT / Data List / MAF.

    6. Read the MAF value displayed on the tester while the engine is idling.

    7. Enter the following menus: Powertrain / Engine and ECT / Active Test / Activate the VSV for EGR Cooler Bypass / Data List / EGR Cooler Bypass Position.

      Tech Tips

      Whether the EGR is passing through the bypass side or cooler side during the Active Test can be confirmed by checking EGR Cooler Bypass Position.

    8. Using the Active Test function, switch the EGR valve bypass switching valve between "Cooler" and "Bypass" a few times, and then check whether the MAF value changes after switching the valve from "Cooler" to "Bypass".

      Tech Tips

      If idling continues for 20 minutes or more, the EGR valve target opening angle becomes 0% (EGR valve fully closed). As this makes diagnosis impossible, it becomes necessary to drive the vehicle or restart the engine.

      Result
      Tester Display Result Proceed to

      Activate the VSV for EGR Cooler Bypass:

      Cooler to Bypass

      		 MAF value does not change A
      MAF value changes B

      Tech Tips

      If the EGR cooler is clogged, the mass air flow changes.


    B

    REPLACE EGR COOLER Click here

    A

  6. CHECK WHETHER DTC OUTPUT RECURS (DTC P0400)


    1. Connect the intelligent tester to the DLC3.

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

    3. Clear the DTCs. Click here

    4. Turn the ignition switch off for 30 seconds or more.

    5. Start the engine and warm it up.

    6. Move the shift lever to 2nd gear and decelerate from a speed of 50 km/h (31 mph) or more (fully release the accelerator for approximately 5 seconds or more).

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

    8. Read the DTCs.

      Tech Tips

      When a DTC is output, the mass air flow meter may be malfunctioning.


    NEXT

    END

  7. REPLACE MASS AIR FLOW METER


    1. Replace the mass air flow meter Click here.

      Tech Tips

      If foreign matter is stuck inside the mass air flow meter, the output characteristics of the mass air flow meter may change, resulting in a malfunction.


    NEXT

    REPLACE EGR COOLER Click here

  8. CHECK FOR DEPOSIT (ELECTRIC EGR CONTROL VALVE ASSEMBLY)


    1. Remove the electric EGR control valve assembly Click here.

    2. Visually check the electric EGR control valve assembly for deposits.

      If there are deposits, clean the electric EGR control valve assembly.

      Note


      • When cleaning the electric EGR control valve, make sure the valve is completely closed.

      • Do not forcibly open the valve, as it may be damaged or deformed.

      • When cleaning the electric EGR control valve, use a piece of cloth soaked with cleaning solvent. Spraying the solvent directly onto these parts or soaking the parts in the solvent may damage the parts.

      • When cleaning the EGR control valve, care should be taken to prevent the ingress of cleaning solvent into the bearings of valve shaft, and when wiping off deposits on the EGR control valve, care should be taken not to push the deposits into the bearings of valve shaft. These contaminants may adversely affect on the function of EGR control valve.

      Tech Tips


      • If the EGR valve does not open properly or is stuck closed, the amount of intake air increases and combustion sounds and engine vibration may increase.

      • If the EGR valve does not close properly or is stuck open, EGR becomes excessive and combustion becomes unstable. Also, there may be a lack of power.

    3. Reinstall the electric EGR control valve assembly Click here.


    NEXT

  9. REPLACE EGR COOLER


    1. Replace the EGR cooler Click here.


    NEXT

  10. CHECK WHETHER DTC OUTPUT RECURS (DTC P0400)


    1. Connect the intelligent tester to the DLC3.

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

    3. Clear the DTCs. Click here

    4. Turn the ignition switch off for 30 seconds or more.

    5. Start the engine and warm it up.

    6. Move the shift lever to 2nd gear and decelerate from a speed of 50 km/h (31 mph) or more (fully release the accelerator for approximately 5 seconds or more).

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

    8. Read the DTCs.

      Tech Tips

      When a DTC is output, the mass air flow meter may be malfunctioning.


    NEXT

    END