ECD SYSTEM(w/ Urea SCR System), 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 assembly

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

  • MAF

  • Target EGR Valve Pos

  • 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).

B001D22E10

CAUTION / NOTICE / HINT

Note

After replacing the ECM, the new ECM needs registration (See page ) and initialization Click here.

Tech Tips

Read freeze frame data using the GTS. 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 GTS to the DLC3.

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

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

    4. Read the DTCs.

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

    B

    GO TO DTC CHART Click here

    A

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


    1. Connect the GTS 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 engine switch off. Wait for 30 seconds, and then restart the engine.

    4. Turn the GTS on.

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

    6. Read the MAF value displayed on the GTS 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 idling the engine, the EGR cooler is bypassed.

      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 (41%)

      • Atmosphere pressure: 101 kPa

      • Engine coolant temperature: 75°C (167°F)

      		 3 to 7 gm/sec
      Closed (0%) 11 to 16 gm/sec

    B

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

    A

  3. READ VALUE USING GTS (ENGINE SPEED AND MAF)


    1. Connect the GTS to the DLC3.

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

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

    4. Start the engine and read the value when 30 seconds has elapsed.

      Standard
      Engine speed MAF
      Idling

      • 3.0 to 15.0 gm/sec (EGR on)

      • 10.0 to 21.0 gm/sec (EGR off)
      Running without load (3000 rpm):

      • 45.0 to 89.0 gm/sec (EGR on)

      • 72.0 to 94.0 gm/sec (EGR off)

    NG

    REPLACE MASS AIR FLOW METER SUB-ASSEMBLY Click here

    OK

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


    1. Connect the GTS 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 engine switch off and wait for 30 seconds.

    4. Start the engine and turn the GTS on.

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

    6. Read the MAF value displayed on the GTS 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.

      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.

      • When operating "Activate the VSV for EGR Cooler Bypass", check that "Cooler" and "Bypass" can be switched between and the EGR cooler by-pass valve regulating link operates. If the link does not operate, the inspection cannot be performed correctly. Therefore, inspect and repair the following parts, perform the Active Test and read the changes in the MAF value.

        - No. 2 EGR valve assembly

        Click here

        - Vacuum hose connection

        Click here

        - No. 1 vacuum switching valve assembly (for EGR Bypass Valve)

        Click here

      Result
      GTS 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 No. 1 EGR cooler is clogged, the mass air flow changes.


    A

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

    B

    REPLACE NO. 1 EGR COOLER Click here

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


    1. Connect the GTS 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 engine switch off and wait for 30 seconds.

    4. Start the engine and turn the GTS on.

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

    6. Read the MAF value displayed on the GTS 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.

      • When operating "Activate the VSV for EGR Cooler Bypass", check that "Cooler" and "Bypass" can be switched between and the EGR cooler by-pass valve regulating link operates. If the link does not operate, the inspection cannot be performed correctly. Therefore, inspect and repair the following parts, perform the Active Test and read the changes in the MAF value.

        - No. 2 EGR valve assembly Click here

        - Vacuum hose connection Click here

        - No. 1 vacuum switching valve assembly (for EGR Bypass Valve) Click here

      Result
      GTS 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 No. 1 EGR cooler is clogged, the mass air flow changes.


    B

    REPLACE NO. 1 EGR COOLER Click here

    A

  6. CHECK WHETHER DTC OUTPUT RECURS (DTC P0400)


    1. Connect the GTS to the DLC3.

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

    3. Clear the DTCs Click here.

    4. Turn the engine 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 / Trouble Codes.

    8. Read the DTCs.

      Tech Tips

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


    NEXT

    END

  7. REPLACE MASS AIR FLOW METER SUB-ASSEMBLY


    1. Replace the mass air flow meter sub-assembly Click here.

      Tech Tips

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


    NEXT

    CHECK WHETHER DTC OUTPUT RECURS (DTC P0400) 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 the function of EGR control valve.

      • When cleaning the electric EGR control valve assembly, perform the initialization procedure.

        Click here

      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 NO. 1 EGR COOLER


    1. Replace the No. 1 EGR cooler Click here.


    NEXT

  10. CHECK WHETHER DTC OUTPUT RECURS (DTC P0400)


    1. Connect the GTS to the DLC3.

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

    3. Clear the DTCs Click here.

    4. Turn the engine 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 / Trouble Codes.

    8. Read the DTCs.

      Tech Tips

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


    NEXT

    END