DTC Troubleshooting

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 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 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 position.
- Vehicle speed at 25 mph(40 km/h) or more, and engine speed between 1,100 rpm and 3,000 rpm.
- 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 - Remove the engine cover, and clean the intake manifold EGR port with throttle plate and induction cleaner, then Go to step 9.

NO - If the screen indicates PASSED, intermittent failure, the system is OK at this time. If the screen indicates EXECUTING, keep driving until a result comes on. If the screen indicates OUT OF CONDITION, Go to step 5 and recheck.

7. Turn the ignition switch OFF.
8. Replace the EGR valve.
9. Turn the ignition switch ON (II).
10. Reset the PCM with the HDS.
11. Do the PCM idle learn procedure.
12. Test-drive under these conditions:
- Engine coolant temperature (ECT SENSOR 1) above 158 °F(70 °C)
- Transmission in D position.
- Vehicle speed at 25 mph(40 km/h) or more, and engine speed between 1,100 rpm and 3,000 rpm.
- During the drive, decelerate (with the throttle fully closed) for 5 seconds

13. Check for Temporary DTCs or DTCs with the HDS.

Is DTC P0401 indicated?

YES - Check for poor connections or loose terminals at the EGR valve and the PCM, then Go to step 1.

NO - Go to step 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. If any other Temporary DTCs or DTCs were indicated in step 13, Go to the indicated DTC's troubleshooting.

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

15. Update the PCM if it does not have the latest software, or substitute a known good PCM.
16. Test-drive under these conditions:
- Engine coolant temperature (ECT SENSOR 1) above 158 °F(70 °C)
- Transmission in D position.
- Vehicle speed at 25 mph(40 km/h) or more, and engine speed between 1,100 rpm and 3,000 rpm.
- During the drive, decelerate (with the throttle fully closed) for 5 seconds

17. Check for Temporary DTCs or 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, then Go to step 16. If the PCM was substituted, Go to step 1.

NO - Go to step 18.

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

Does the screen indicate PASSED?

YES - If the PCM was updated, troubleshooting is complete. If the PCM was substituted, replace the original PCM. If any other Temporary DTCs or DTCs were indicated in step 17, Go to the indicated DTC's troubleshooting.

NO - If the screen 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, then Go to step 16. If the PCM was substituted, Go to step 1. If the screen indicates NOT COMPLETED, Go to step 16.