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ECD SYSTEM(w/o DPF), Diagnostic DTC:P0400

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DTC Code DTC Name
P0400 Exhaust Gas Recirculation Flow
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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.

Table 1. P0400
DTC Detection Drive Pattern DTC Detection Condition Trouble Area
Vehicle driving at an engine speed of 1000 to 1800 rpm for 30 minutes

All of following conditions are met


  • Drive the vehicle at a constant speed

  • The actual mass air flow rate output differs from the estimated mass air flow rate more than the threshold for 30 minutes.

(2 trip detection logic)

  • EGR valve deposit

  • EGR valve passage deposit

  • EGR with cooler pipe assembly

  • Mass air flow meter
Table 2. Related Data List
DTC No. Data List
P0400

  • MAF

  • Target EGR Position

  • Actual EGR Valve Pos.
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MONITOR DESCRIPTION

The ECM determines that the electric EGR control valve assembly is malfunctioning. The ECM then illuminates the MIL (2 trip detection logic).

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CAUTION / NOTICE / HINT

Note:

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

Tip:

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.

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PROCEDURE


  1. Click here

    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.

      Table 3. Result
      Result Proceed to
      P0400 is output A
      P0400 and other DTCs are output B

  2. Click here

    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.

      Tip:

      • 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.

      Table 4. Result
      Tester Display 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.

      Tip:

      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 vacuum regulating valve assembly or mass air flow meter.

      Standard
      EGR Valve Condition (Opening) Measuring Condition MAF
      Open (56%)

      • Atmosphere pressure: 101 kPa

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

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

      		 3.5 to 7 gm/sec
      Closed (0%) 8 to 12 gm/sec

  3. Click here

    CHECK MASS AIR FLOW METER


    1. Perform mass air flow meter On-Vehicle Inspection (Click here).


  4. Click here

    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 to ON 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 EGR Cooler Bypass / Data List / EGR Cooler Bypass Position.

      Tip:

      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 0% and 100% a few times, and then check whether the MAF value changes.

      Tip:

      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.

      Table 5. Result
      Tester Display Result Proceed to

      Activate the EGR Cooler Bypass:

      0 to 100%

      		 MAF value does not change A
      MAF value changes B
      Tip:

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

      • When confirming the change in the MAF value, "Active test the EGR Cooler Bypass" of the Active Test should be 0% and 100%.


  5. Click here

    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 EGR Cooler Bypass / Data List / EGR Cooler Bypass Position.

      Tip:

      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 0% and 100% a few times, and then check whether the MAF value changes.

      Tip:

      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.

      Table 6. Result
      Tester Display Result Proceed to

      Activate the EGR Cooler Bypass:

      0 to 100%

      		 MAF value does not change A
      MAF value changes B
      Tip:

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

      • When confirming the change in the MAF value, "Active test the EGR Cooler Bypass" of the Active Test should be 0% and 100%.


  6. Click here

    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. Drive the vehicle at an engine speed of 1000 to 1800 rpm for 30 minutes or more.

      CAUTION:

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

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

    8. Read the pending DTCs.

      Tip:

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


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  7. Click here

    REPLACE MASS AIR FLOW METER


    1. Replace the mass air flow meter (Click here).


  8. Click here

    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.

      Tip:

      • 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.


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    REPLACE EGR WITH COOLER PIPE SUB-ASSEMBLY


    1. Replace the EGR cooler (Click here).


  10. Click here

    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. Drive the vehicle at an engine speed of 1000 to 1800 rpm for 30 minutes or more.

      CAUTION:

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

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

    8. Read the pending DTCs.

      Tip:

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


    • NEXT

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