DTC Troubleshooting

Control System DTCs

DTC Troubleshooting: P0401

DTC P0401 : EGR Insufficient Flow

NOTE: Before you troubleshoot, record all freeze data and any on-board snapshot, and review the general troubleshooting information How To Troubleshoot The Fuel And Emissions Systems.

1. EGR valve check:

EGR valve check
-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 (A/T in P or N, M/T in neutral) until the radiator fan comes on, then let it idle.

-4. Do the EGR TEST with the HDS.

Is the result OK?
-YES- Go to step 2.
-NO- Replace the EGR valve Service and Repair, then do the repair verification.

2. Problem verification:

Problem verification
-1. Test-drive under these conditions:
* Engine coolant temperature (ECT SENSOR 1) above 158 °F (70 °C)
* A/T in D, M/T in 4th
* Drive the vehicle at a steady speed between 15-75 mph (24-120 km/h) for at least 5 seconds
* 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 5 seconds

-2. Monitor the OBD STATUS for DTC P0401 with the HDS.

Does the HDS indicate FAILED?
-YES- Clean the intake manifold EGR port with throttle plate cleaner. Also, clean the passage inside the EGR valve with throttle plate cleaner, then do the repair verification.
-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 ECM/PCM. If the HDS indicates EXECUTING, keep driving until a result comes on. If the HDS indicates OUT OF CONDITION, go to step 2-1 on this step and recheck.

Repair verification (OBD STATUS check):

-1. Turn the ignition switch to LOCK (0).

-2. Reconnect all connectors.

-3. Turn the ignition switch to ON (II).

-4. Reset the ECM/PCM with the HDS How To Troubleshoot The Fuel And Emissions Systems.

-5. Do the ECM/PCM idle learn procedure ECM/PCM Idle Learn Procedure.

-6. Test-drive under these conditions:
* Engine coolant temperature (ECT SENSOR 1) above 158 °F (70 °C)
* A/T in D, M/T in 4th
* Drive the vehicle at a steady speed between 15-75 mph (24-120 km/h) for at least 5 seconds
* 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 5 seconds

-7. Monitor the OBD STATUS for DTC P0401 in the DTCs MENU with the HDS.

Does the HDS indicate PASSED, FAILED, EXECUTING, or OUT OF CONDITION?
-PASSED- Troubleshooting is complete. If any other Pending or Confirmed DTCs were indicated, go to the indicated DTC's troubleshooting.
-FAILED- Go to step 1 and recheck.
-EXECUTING- Keep the test condition until a result comes on.
-OUT OF CONDITION- Meet the test condition, and check the OBD STATUS again.