2012 Honda Insight BaseFACTORY OEM SERVICE PROCEDURE

DTC P0401: EGR Insufficient Flow

NOTE: Before you troubleshoot, record all freeze data and any on-board snapshot, and review the general troubleshooting information (see GENERAL TROUBLESHOOTING INFORMATION ).
  1. Turn the ignition switch to ON (II).
  2. Clear the DTC with the HDS.
  3. Start the engine. Hold the engine speed at 3, 000 rpm without load (in P or N) until the radiator fan comes on, then let it idle.
  4. Do the EGR TEST in the INSPECTION MENU with the HDS.

    Is the result OK? 

    YES  -Go to step 5.

    NO  -Go to step  7.

  5. Test-drive under these conditions:
    • Engine coolant temperature (ECT SENSOR 1) above 158°F(70°C)
    • Transmission in D
    • Drive the vehicle at a steady speed between 55-75 mph (90-120 km/h) for at least 10 seconds
    • During the drive, decelerate (with the throttle fully closed) for at least 4 seconds
  6. Monitor the OBD STATUS for DTC P0401 in the DTCs MENU with the HDS.

    Does the HDS indicate FAILED? 

    YES  -Clean the intake manifold EGR port and EGR pipe (see EGR PIPE REMOVAL AND INSTALLATION ) with throttle plate cleaner. Also, clean the passage inside the EGR valve with throttle plate cleaner, then go to step  9.

    NO  -If the HDS indicates PASSED, intermittent failure, the system is OK at this time. Check for poor connections or loose terminals at the EGR valve and the PCM. If the HDS indicates EXECUTING, keep driving until a result comes on. If the HDS indicates OUT OF CONDITION, go to step  5 and recheck.

  7. Turn the ignition switch to LOCK (0).
  8. Replace the EGR valve (see EGR VALVE REPLACEMENT ).
  9. Turn the ignition switch to ON (II).
  10. Reset the PCM with the HDS.
  11. Do the PCM idle learn procedure (see PCM IDLE LEARN PROCEDURE ).
  12. Test-drive under these conditions:
    • Engine coolant temperature (ECT SENSOR 1) above 158°F(70°C)
    • Transmission in D
    • Drive the vehicle at a steady speed between 55-75 mph (90-120 km/h) for at least 10 seconds
    • During the drive, decelerate (with the throttle fully closed) for at least 4 seconds
  13. Check for Pending or Confirmed DTCs with the HDS.

    Is DTC P0401 indicated? 

    YES  -Check for poor connections or loose terminals at the EGR valve and the PCM. If the connections and the terminals are OK, go to step  15.

    NO  -Go to step 14.

  14. Monitor the OBD STATUS for DTC P0401 in the DTCs MENU with the HDS.

    Does the HDS indicate PASSED? 

    YES  -Troubleshooting is complete. If any other Pending or Confirmed DTCs were indicated in step  13, go to the indicated DTC'S TROUBLESHOOTING .

    NO  -If the HDS indicates FAILED, check for poor connections or loose terminals at the EGR valve and the PCM, then go to step  1. If the HDS indicates EXECUTING, keep driving until a result comes on. If the HDS indicates OUT OF CONDITION, go to step  12.

  15. Update the PCM if it does not have the latest software (see PCM UPDATE ), or substitute a known-good PCM (see SUBSTITUTING THE PCM ).
  16. Test-drive under these conditions:
    • Engine coolant temperature (ECT SENSOR 1) above 158°F(70°C)
    • Transmission in D
    • Drive the vehicle at a steady speed between 55-75 mph (90-120 km/h) for at least 10 seconds
    • During the drive, decelerate (with the throttle fully closed) for at least 4 seconds
  17. Check for Pending or Confirmed DTCs with the HDS.

    Is DTC P0401 indicated? 

    YES  -Check for poor connections or loose terminals at the EGR valve and the PCM. If the PCM was updated, substitute a known-good PCM (see SUBSTITUTING THE PCM ), then go to step  16. If the PCM was substituted, go to step  1.

    NO  -Go to step 18.

  18. Monitor the OBD STATUS for DTC P0401 in the DTCs MENU with the HDS.

    Does the HDS indicate PASSED? 

    YES  -If the PCM was updated, troubleshooting is complete. If the PCM was substituted, replace the original PCM (see PCM REPLACEMENT ). If any other Pending or Confirmed DTCs were indicated in step  17, go to the indicated DTC'S TROUBLESHOOTING .

    NO  -If the HDS indicates FAILED, check for poor connections or loose terminals at the EGR valve and the PCM. If the PCM was updated, substitute a known-good PCM (see SUBSTITUTING THE PCM ), then go to step  16. If the PCM was substituted, go to step  1. If the HDS indicates EXECUTING, keep driving until a result comes on. If the HDS indicates OUT OF CONDITION, go to step  16.

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When to See a Mechanic

Stop DIY work and contact a certified mechanic immediately if any of the following apply:

  • • You smell fuel, burning insulation, or see smoke.
  • • Brakes feel soft, pull hard to one side, or make grinding noises.
  • • The engine overheats, stalls repeatedly, or misfires under load.
  • • You are missing required tools, torque specs, or safe lifting equipment.
  • • You are not confident in the next step or safety outcome.