DTC Troubleshooting: P0401 (80)

DTC P0401:  EGR Insufficient Flow


NOTE: Before you troubleshoot, record all freeze data and any on-board snapshot, and review the general troubleshooting information.

1.Turn the ignition switch ON (II).

2.Clear the DTC with the HDS.

3.Start the engine. Hold the engine speed at 3,000 rpm (min-1) without 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 HDS.

Is the result OK?


YES - Go to 5.


NO - Go to 7.


5.Test-drive under these conditions:
  • ECT SENSOR 1 above 70 °C (158 °F)
  • A/T in D position (M/T in 4th gear)
  • Vehicle speed at 50 km/h (31 mph) or more, and engine speed between 1,200 and 3,600 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 HDS.

Does the screen indicate FAILED?


YES - Clean the intake manifold EGR port, and the EGR pipe with throttle plate and induction cleaner. Also, clean the passage inside the EGR valve with throttle plate and induction cleaner, then go to 9.


NO - If the screen indicates PASSED, intermittent failure, system is OK at this time. Check for poor connections or loose terminals at the EGR valve and the ECM/PCM. If the screen indicates EXECUTING, keep driving until a result comes on. If the screen indicates 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.Reset the ECM/PCM with the HDS.

11.Do the ECM/PCM idle learn procedure.

12.Test-drive under these conditions:
  • ECT SENSOR 1 above 70 °C ( 158 °F)
  • A/T in D position (M/T in 4th gear)
  • Vehicle speed at 50 km/h (31 mph) or more, and engine speed between 1,200 and 3,600 rpm (min-1)
  • During the drive, decelerate (with the throttle fully closed) for 5 seconds

13.Check for Temporary DTCs or DTCs with 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. If the connections are OK, go to 15. If any other Temporary DTCs or DTCs are indicated, go to the indicated DTC's troubleshooting.


NO - Go to 14.


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

Does the screen indicate PASSED?


YES - Troubleshooting is complete.n


NO - If the screen indicates FAILED, go to 1 and recheck. If the screen indicates EXECUTING, keep driving until a result comes on. If the screen indicates 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 these conditions:
  • ECT SENSOR 1 above 70 °C (158 °F)
  • A/T in D position (M/T in 4th gear)
  • Vehicle speed at 50 km/h (31 mph) or more, and engine speed between 1,200 and 3,600 rpm (min-1)
  • During the drive, decelerate (with the throttle fully closed) for 5 seconds

17.Check for Temporary DTCs or DTCs with 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's troubleshooting.


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