DTC Troubleshooting: P0401 (80)

DTC P0401:  EGR Insufficient Flow


1.Turn the ignition switch ON (II).

2.Do the DTC CLEAR in the CLEAR MENU with the Honda PGM Tester or the HDS.

3.Start the engine. Hold the engine speed at 3,000 rpm (min-1) with no load (in Park or neutral) until the radiator fan comes on, then let it idle.

4.Do the EGR TEST in the INSPECTION MENU with the Honda PGM Tester or the HDS.

Is the result OK?


YES - Go to 5.


NO - Go to 7.


5.Test-drive under the following conditions.
  • Engine coolant temperature more than 70°C (158°F)
  • Transmission in 4th gear (A/T in D position)
  • Vehicle speed at 40 km/h (25 mph) or more, and engine speed between 1,100 rpm (min-1) and 3,000 rpm (min-1)
  • During the drive, decelerate (with the throttle fully closed) for 5 seconds

6.Monitor the OBD STATUS for DTC P0401 in the DTCs MENU with the Honda PGM Tester or the HDS.

Is it FAILED?


YES - Remove the EGR Plate and clean the intake manifold port with carburetor cleaner, then go to 9.


NO - If it is PASSED, intermittent failure, system is OK at this time. If it is EXECUTING, keep the driving condition continually until a result comes on. If it is Out of CONDITION, go to 5 and recheck.


7.Turn the ignition switch OFF.

8.Replace the EGR valve.

9.Turn the ignition switch ON (II).

10.Do the ECM/PCM RESET in the CLEAR MENU with the Honda PGM Tester or the HDS.

11.Do the ECM/PCM idle learn procedure.

12.Test-drive under the following conditions.
  • Engine coolant temperature more than 70°C (158°F)
  • Transmission in 4th gear (A/T in D position)
  • Vehicle speed at 40 km/h (25 mph) or more, and engine speed between 1,100rpm (min-1) and 3,000rpm (min-1)
  • During the drive, decelerate (with the throttle fully closed) for 5 seconds

13.Check for Temporary DTCs or DTCs in the DTCs MENU with the Honda PGM Tester or the HDS.

Are any Temporary DTCs or DTCs indicated?


YES - If DTC P0401 is indicated, check for poor connections or loose terminals at the EGR valve and the ECM/PCM, then go to 1. If connections are OK, go to 15. If any other Temporary DTCs or DTCs are indicated, go to the indicated DTC troubleshooting.


NO - Go to 14.


14.Monitor the OBD STATUS for DTC P0401 in the DTCs MENU with the Honda PGM Tester or the HDS.

Is it PASSED?


YES - Troubleshooting is complete.n


NO - If it is FAILED, then go to 1. and recheck. If it is EXECUTING, keep the driving condition continually until a result comes on. If it is Out of CONDITION, go to 12 and recheck.

15.Update the ECM/PCM if it does not have the latest software, or substitute a known-good ECM/PCM.

16.Test-drive under the following conditions.
  • Engine coolant temperature more than 70°C (158°F)
  • Transmission in D position
  • Vehicle speed at 40 km/h (25 mph) or more, and engine speed between 1,100 rpm (min-1) and 3,000 rpm (min-1)
  • During the drive, decelerate (with the throttle fully closed) for 5 seconds

17.Check for Temporary DTCs or DTCs in the DTCs MENU with the Honda PGM Tester or the HDS.

Are any Temporary DTCs or DTCs indicated?


YES - If DTC P0401 is indicated, check for poor connections or loose terminals at the EGR valve and the ECM/PCM, then go to 1. If any other Temporary DTCs or DTCs are indicated, go to the indicated DTC troubleshooting.


NO - If the ECM/PCM was updated, troubleshooting is complete. If the ECM/PCM was substituted, replace the original ECM/PCM