Diagnostic Procedure

DTC P0401 DIAGNOSTIC PROCEDURE TABLE

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 system related) been recorded?	Yes	Go to the next step.
1		No	Record FREEZE FRAME DATA and DIAGNOSTIC MONITORING TEST RESULTS on the repair order, then go to the next step.
2	VERIFY RELATED REPAIR INFORMATION AVAILABILITY Verify related Service Bulletins and/or on-line 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 the ignition switch off then to the ON position (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 Inspect the EGR valve. (See EGR VALVE INSPECTION .) Is the EGR valve normal?	Yes	Go to the next step.
5		No	Replace the EGR valve, then go to Step 8. (See EGR VALVE REMOVAL/INSTALLATION .)
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. (See MANIFOLD ABSOLUTE PRESSURE (MAP) SENSOR REMOVAL/INSTALLATION .)
7	INSPECT EGR VALVE PASSAGE Turn the ignition switch off. Remove the 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 DTC from PCM memory using WDS or equivalent. Run PCM Adaptive Memory Procedure Drive Mode. (See PCM ADAPTIVE MEMORY PRODUCTION DRIVE MODE .) Stop vehicle and access ON BOARD READINESS TEST to inspect DRIVE MODE completion status. Verify FUEL_EVAL and EGR__EVAL PIDs status. Does FUEL_EVAL and EGR_EVAL PIDs change to Yes?	Yes	Go to the next step.
8		No	Retry this step.
9	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 pressure variation) value. Is value within the specification?	Yes	Go to the next step.
9		No	Replace the PCM, then go to the next step. (See PCM REMOVAL/INSTALLATION .)
10	VERIFY AFTER REPAIR PROCEDURE Perform "AFTER REPAIR PROCEDURE". (See AFTER REPAIR PROCEDURE .) Is there any DTC present?	Yes	Go to the applicable DTC inspection. (See DTC TABLE .)
10		No	Troubleshooting completed.