DTC P0401

id010200815300

DTC P0401

EGR flow insufficient detected

DETECTION CONDITION

• The PCM monitors the difference in intake manifold pressures when the EGR is operated and stopped. If the difference is the small, the PCM determines that the EGR flow is insufficient.
Diagnostic support note
• This is an intermittent monitor. (EGR system)
• The MIL illuminates if PCM detects the above malfunctioning condition in two consecutive drive cycles or in one drive cycle while the DTC for the same malfunction has been stored in the PCM.
• The PENDING CODE is available if the PCM detects the above malfunction conditions during the first drive cycle.
• The FREEZE FRAME DATA is available.
• The DTC is stored in the PCM memory.

POSSIBLE CAUSE

• EGR valve malfunction
• MAP sensor malfunction
• Vacuum hoses improper connection
• PCM malfunction

Diagnostic procedure

STEP

INSPECTION

ACTION

1
PERFORM DTC CONFIRMATION PROCEDURE
• Perform the DTC CONFIRMATION PROCEDURE.
• Is the same DTC present?
Yes
Go to the next step.
No
Intermittent concern exists.
Go to INTERMITTENT CONCERN TROUBLESHOOTING procedures.
2
VERIFY RELATED PENDING CODE OR STORED DTCs
• Turn the ignition switch off, then to the ON position (Engine off).
• Verify the related PENDING CODE or stored DTCs.
• Are other DTCs present?
Yes
Go to the appropriate DTC troubleshooting procedures.
No
Go to the next step.
3
VERIFY TRIGGER DTC FOR FREEZE FRAME DATA
• Is DTC P0401 displayed in FREEZE FRAME DATA?
Yes
Go to the next step.
No
Go to troubleshooting procedures for the DTC on the FREEZE FRAME DATA.
4
INSPECT VACUUM HOSE CONDITION
• Inspect vacuum hoses for clogs, any damage, freezing, or vacuum leakage.
• Is there any malfunction?
Yes
Replace the vacuum hoses, then go to Step 8.
No
Go to the next step.
5
INSPECT EGR VALVE MALFUNCTION
• Inspect the EGR valve.
• Is the EGR valve normal?
Yes
Go to the next step.
No
Replace the EGR valve, then go to Step 8.
6
INSPECT MAP SENSOR MALFUNCTION
• Perform the MAP sensor inspection.
• Is MAP sensor normal?
Yes
Go to the next step.
No
Replace the MAP sensor, then go to Step 8.
7
INSPECT EGR VALVE PASSAGE
• Turn the ignition switch off.
• Remove the EGR valve.
• Inspect the following:
- Gasket installation
- EGR valve stuck open or closed
- EGR valve clogging
- EGR passage clogging
• Are there any malfunction?
Yes
Repair or replace the malfunctioning parts, then go to the next step.
No
Go to the next step.
8
VERIFY TROUBLESHOOTING OF DTC P0401 COMPLETED
• Make sure to reconnect all disconnected connectors.
• Clear the DTC from the PCM memory using the WDS or equivalent.
• Perform the KOER self-test.
• Is the same DTC present?
Yes
Replace the PCM, then go to the next step.
No
Go to the next step.
9
VERIFY AFTER REPAIR PROCEDURE
• Perform the "AFTER REPAIR PROCEDURE".
• Are any DTCs present?
Yes
Go to the applicable DTC inspection.
No
DTC troubleshooting completed.