Diagnostic Procedure

DTC P0401 DIAGNOSTIC PROCEDURE

STEP	INSPECTION		ACTION
1	VERIFY FREEZE FRAME DATA AND DIAGNOSTIC MONITORING TEST RESULTS HAVE BEEN RECORDED Have FREEZE FRAME DATA and DIAGNOSTIC MONITORING TEST RESULTS (EGR related) been recorded?	Yes	Go to the next step.
1		No	Record FREEZE FRAME DATA and DIAGNOSTIC MONITORING TEST RESULTS on repair order, then go to the next step.
2	VERIFY RELATED REPAIR INFORMATION AVAILABILITY Check for related Service Bulletins and/or online repair information availability. Is any related repair information available?	Yes	Perform repair or diagnosis according to the available repair information. If the vehicle is not repaired, go to the next step.
2		No	Go to the next step.
3	INSPECT FOR OTHER DTCS Turn ignition switch to OFF then ON (Engine off). Have other DTCs been stored?	Yes	Repair circuit malfunction for applicable DTCs.
3		No	Go to the next step.
4	INSPECT VACUUM HOSE CONDITION Inspect vacuum hoses for clogs, any damages, frozen, or vacuum leakage. Is there any malfunction?	Yes	Replace vacuum hoses, then go to Step 8.
4		No	Go to the next step.
5	INSPECT EGR VALVE MALFUNCTION Perform EGR valve inspection. (See EGR VALVE INSPECTION ). Is EGR valve normal?	Yes	Go to the next step.
5		No	Replace EGR valve, then go to Step 8.
6	INSPECT MAP SENSOR MALFUNCTION Perform MAP sensor inspection. (See MANIFOLD ABSOLUTE PRESSURE (MAP) SENSOR INSPECTION ). Is EGR valve normal?	Yes	Go to the next step.
6		No	Replace MAP sensor, then go to Step 8.
7	INSPECT EGR VALVE PASSAGE Turn the ignition switch off. Remove EGR valve. Is gasket installation normal?	Yes	Go to the next step.
7		No	Install gasket correctly, then go to the next step.
8	MONITOR EGR SYSTEM BY DRIVE MODE Clear the DTC from the PCM memory using the WDS or equivalent. Run DRIVE MODE 1. (See OBD-II DRIVE MODE ). Stop vehicle and access ON BOARD READINESS TEST to inspect DRIVE MODE completion status. Verify FUEL_EVAL PID status. Does FUEL_EVAL PID change to Yes?	Yes	Retry this step.
8		No	Go to the next step.
9	MONITOR EGR SYSTEM BY DRIVE MODE Run DRIVE MODE 2. (See EGR SYSTEM REPAIR VERIFICATION DRIVE MODE ). Stop vehicle and access ON BOARD SYSTEM READINESS TEST to inspect DRIVE MODE completion status. Verify EGR_EVAL PID status. Does EGR_EVAL PID change to Yes?	Yes	Go to the next step.
9		No	Retry this step.
10	VERIFY TROUBLESHOOTING OF DTC P0401 COMPLETED Make sure to reconnect all disconnected connectors. Access DIAGNOSTIC MONITORING TEST RESULTS. (See DIAGNOSTIC MONITORING TEST RESULTS ACCESS PROCEDURE ). Verify TEST #10: 31: 83 (EGR flow test) value. Is value within specification?	Yes	Go to the next step.
10		No	Replace PCM, then go to the next step.
11	VERIFY AFTER REPAIR PROCEDURE Perform the "After Repair Procedure". (See AFTER REPAIR PROCEDURE ). Is any DTC present?	Yes	Go to the applicable DTC inspection. (See DTC TABLE ).
11		No	Troubleshooting completed.