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 to ON (II).
  1. Clear the DTC with the HDS.
  1. Start the engine. Hold the engine speed at 3,000 rpm (min −1 ) without load (in neutral) until the radiator fan comes on, then let it idle.
  1. 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 .
  1. Test-drive under these conditions:
    • Engine coolant temperature (ECT SENSOR 1) above 70 °C (158 °F)
    • Transmission in 4th gear
    • Drive the vehicle at a steady speed between 80−120 km/h (55−75 mph) for 10 seconds or more
    • During the drive, decelerate (with the throttle fully closed) for 5 seconds
  1. 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 Step 9 .
NO -
If the screen indicates PASSED, intermittent failure, the system is OK at this time. Check for poor connections or loose terminals at the EGR valve and the ECM. 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.
  1. Turn the ignition switch to LOCK (0).
  1. Replace the EGR valve.
  1. Turn the ignition switch to ON (II).
  1. Reset the ECM with the HDS.
  1. Do the ECM idle learn procedure.
  1. Test-drive under these conditions:
    • Engine coolant temperature (ECT SENSOR 1) above 70 °C (158 °F)
    • Transmission in 4th gear
    • Drive the vehicle at a steady speed between 80−120 km/h (55−75 mph) for 10 seconds or more
    • During the drive, decelerate (with the throttle fully closed) for 5 seconds
  1. 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 ECM, then go to Step 1 .
NO -
Go to Step 14 .
  1. 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 ECM, 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 .
  1. Update the ECM if it does not have the latest software, or substitute a known-good ECM.
  1. Test-drive under these conditions:
    • Engine coolant temperature (ECT SENSOR 1) above 70 °C (158 °F)
    • Transmission in 4th gear
    • Drive the vehicle at a steady speed between 80−120 km/h (55−75 mph) for 10 seconds or more
    • During the drive, decelerate (with the throttle fully closed) for 5 seconds
  1. 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 ECM. If the ECM was updated, substitute a known-good ECM, then go to Step 16 . If the ECM was substituted, go to Step 1 .
NO -
Go to Step 18 .
  1. Monitor the OBD STATUS for DTC P0401 in the DTCs MENU with the HDS.
Does the screen indicate PASSED?
YES -
If the ECM was updated, troubleshooting is complete. If the ECM was substituted, replace the original ECM. 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 ECM. If the ECM was updated, substitute a known-good ECM, then go to Step 16 . If the ECM was substituted, 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 16 .