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DTC P0404 (19-21 9-Speed A/T)

DTC P0404  : Exhaust Gas Recirculation (EGR) Valve Circuit Range/Performance Problem

NOTE:  Before you troubleshoot, review the general troubleshooting information - Refer to: How to Troubleshoot the Fuel and Emissions Systems .

DTC Description Confirmed DTC Pending DTC
P0404 Exhaust Gas Recirculation (EGR) Valve Circuit Range/Performance Problem    

DTC (PGM-FI)

  1. Problem verification

    - 1. Turn the vehicle to the ON mode.

    - 2. Clear the DTC with the HDS.

    - 3. Turn the vehicle to the OFF (LOCK) mode.

    - 4. Start the engine.

    - 5. Hold the engine speed at 3, 000 rpm without load (in P or N) until the radiator fan comes on, then let it idle.

    - 6. Do the EGR TEST with the HDS.

    EGR TEST

    Is the result OK?

    YES 

    Intermittent failure, the system is OK at this time. Clean any carbon build-up on the EGR valve with throttle plate cleaner. If the on-board snapshot of this DTC is recorded, try to reproduce the failure under the same conditions with the on-board snapshot - Refer to: How to Troubleshoot the Fuel and Emissions Systems .

    NO 

    The failure is duplicated. Go to step 2.

  2. EGR valve position sensor internal circuit check

    - 1. Turn the vehicle to the OFF (LOCK) mode.

    - 2. Disconnect the following connector.

    EGR valve 5P connector

    - 3. At the EGR valve side, measure the resistance between test points 1 and 2.

    Test condition
         		 Vehicle OFF (LOCK) mode
    EGR valve 5P connector: disconnected
    Test point 1 EGR valve 5P connector (male terminals) No. 3 (valve side):
    Test point 2 EGR valve 5P connector (male terminals) No. 4 (valve side):
    GHH307563Courtesy of HONDA, U.S.A., INC.

    Is there 100 kΩ or more?

    YES 

    Replace the EGR valve .

    NO 

    Go to step 3.

  3. EGR valve internal circuit check

    - 1. At the EGR valve side, measure the resistance between test point 1 and 2.

    Test condition Vehicle OFF (LOCK) mode
    EGR valve 5P connector: disconnected
    Test point 1 EGR valve 5P connector (male terminals) No. 2 (valve side):
    Test point 2 EGR valve 5P connector (male terminals) No. 4 (valve side):
    GHH307564Courtesy of HONDA, U.S.A., INC.

    Is there 100 kΩ or more?

    YES 

    Replace the EGR valve .

    NO 

    Go to step 4.

  4. Open wire check (E-EGR PG line)

    - 1. Check for continuity between test point 1 and 2.

    Test condition Vehicle OFF (LOCK) mode
    EGR valve 5P connector: disconnected
    Test point 1 EGR valve 5P connector (female terminals) No. 1:
    Test point 2 Body ground
    GHH307565Courtesy of HONDA, U.S.A., INC.

    Is there continuity?

    YES 

    The E-EGR PG wire is OK. Go to step 5.

    NO 

    Repair an open in the E-EGR PG wire between the EGR valve and G101.

  5. Shorted wire check (E EGR line)

    - 1. Jump the SCS line with the HDS, and wait more than 1 minute.

    - 2. Disconnect the following connector.

    PCM connector E (80P)

    - 3. Check for continuity between test points 1 and 2.

    Test condition Vehicle OFF (LOCK) mode
    EGR valve 5P connector: disconnected
    PCM connector E (80P): disconnected
    Test point 1 PCM connector E (80P) No. 28 - Refer to:
    PCM Connector for Inputs and Outputs (9-Speed A/T) (2019 2020 2021) .
    Test point 2 Body ground

    Is there continuity?

    YES 

    Repair a short in the E EGR wire between the PCM (E28) and the EGR valve.

    NO 

    The E EGR wire is not shorted. Go to step 6.

  6. Open wire check (E EGR line)

    - 1. Check for continuity between test points 1 and 2.

    Test condition Vehicle OFF (LOCK) mode
    EGR valve 5P connector: disconnected
    PCM connector E (80P): disconnected
    Test point 1 EGR valve 5P connector (female terminals) No. 5:
    Test point 2 PCM connector E (80P) No. 28 - Refer to:
    PCM Connector for Inputs and Outputs (9-Speed A/T) (2019 2020 2021)
    GHH307566Courtesy of HONDA, U.S.A., INC.

    Is there continuity?

    YES 

    The E EGR wire is OK. Go to step 7.

    NO 

    Repair an open in the E EGR wire between the PCM (E28) and the EGR valve.

  7. EGR port and passage cleaning

    - 1. Remove the EGR valve.

    - 2. Clean the intake manifold EGR port with throttle plate cleaner. Also, clean the passage inside the EGR valve with throttle plate cleaner.

    - 3. Install the EGR valve.

    - 4. Reconnect all connectors.

    - 5. Turn the vehicle to the ON mode.

    - 6. Reset the PCM with the HDS.

    Reset PCM

    - 7. Do the PCM idle learn procedure.

    - 8. Do the EGR TEST with the HDS.

    EGR TEST

    Is the result OK?

    YES 

    The failure is not duplicated.

    NO 

    Go to step 8.

  8. EGR valve check

    - 1. Substitute a known-good EGR valve.

    - 2. Reconnect all connectors.

    - 3. Turn the vehicle to the ON mode.

    - 4. Reset the PCM with the HDS.

    Reset PCM

    - 5. Do the PCM idle learn procedure.

    - 6. Do the EGR TEST with the HDS.

    EGR TEST

    Is the result OK?

    YES 

    Replace the original EGR valve .

    NO 

    The EGR valve is OK. Check for any authorized service information related to the DTCs or symptoms you are troubleshooting, or substitute a known-good PCM - Refer to: PCM Removal and Installation (9-Speed A/T) (2019 2020 2021) , then recheck. If DTC P0404 goes away and the PCM was substituted, replace the original PCM - Refer to: PCM Removal and Installation (9-Speed A/T) (2019 2020 2021) .

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