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 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 key 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 9.
4		No	Go to the next step.
5	INSPECT EGR VALVE MALFUNCTION Perform EGR valve inspection. (See EGR VALVE INSPECTION ) Is EGR valve okay?	Yes	Go to the next step.
5		No	Replace EGR valve, then go to Step 9.
6	INSPECT EGR BOOST SENSOR MALFUNCTION Perform EGR boost sensor inspection. (See EGR BOOST SENSOR INSPECTION ) Is EGR valve okay?	Yes	Go to the next step.
6		No	Replace EGR boost sensor, then go to Step 9.
7	INSPECT EGR BOOST SENSOR SOLENOID VALVE Perform EGR boost sensor solenoid valve inspection. (See EGR BOOST SENSOR SOLENOID VALVE INSPECTION ) Is EGR valve okay?	Yes	Replace EGR boost sensor solenoid valve, then go to Step 9.
7		No	Go to the next step.
8	INSPECT EGR VALVE PASSAGE Turn the ignition switch off. Remove EGR valve. Is gasket installation normal?	Yes	Go to the next step.
8		No	Install gasket correctly, then go to the next step.
9	MONITOR EGR SYSTEM BY DRIVE MODE Clear the DTC from the PCM memory using the WDS or equivalent. Run Drive Mode 1 (See MODE 1 (PCM ADAPTIVE MEMORY PRODUCE DRIVE MODE) .) Access RFC FLAG PID using the WDS or equivalent. Is RFC FLAG PID OFF?	Yes	Retry this step.
9		No	Go to the next step.
10	MONITOR EGR SYSTEM BY DRIVE MODE Run Drive Mode 2. (See MODE 2 (EGR SYSTEM REPAIR VERIFICATION DRIVE MODE) WITH REAR HO2S MODEL .) Check EGR System Monitor is checked using On-Board Readiness Test function. Has EGR system been monitored?	Yes	Go to the next step.
10		No	Retry this step.
11	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 ID 10: 31: 83 (EGR flow test) value. Is value within specification?	Yes	Go to the next step.
11		No	Replace PCM, then go to the next step.
12	VERIFY AFTER REPAIR PROCEDURE Perform the "After Repair Procedure". (See AFTER REPAIR PROCEDURE .) Are any DTCs present?	Yes	Go to the applicable DTC inspection. (See DTC TABLE .)
12		No	Troubleshooting completed.

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 SERVICE INFORMATION AVAILABILITY Check for related Service Information availability. Is any related Service Information available?	Yes	Perform repair or diagnosis according to available Service Information. If vehicle is not repaired, go to next step.
2		No	Go to next step.
3	INSPECT FOR OTHER DTCS Turn the ignition switch off then ON (Engine OFF). Have other DTCs been stored?	Yes	Repair circuit malfunction for applicable DTCs.
3		No	Go to 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 9.
4		No	Go to next step.
5	INSPECT EGR VALVE MALFUNCTION Perform EGR valve inspection. (See EGR VALVE INSPECTION ) Is EGR valve normal?	Yes	Go to next step.
5		No	Replace EGR valve, then go to Step 9.
6	INSPECT EGR BOOST SENSOR MALFUNCTION Perform EGR boost sensor inspection. (See EGR BOOST SENSOR INSPECTION ) Is EGR valve normal?	Yes	Go to next step.
6		No	Replace EGR boost sensor, then go to Step 9.
7	INSPECT EGR BOOST SENSOR SOLENOID VALVE Perform EGR boost sensor solenoid valve inspection. (See EGR BOOST SENSOR SOLENOID VALVE INSPECTION ) Is EGR valve normal?	Yes	Replace EGR boost sensor solenoid valve, then go to Step 9.
7		No	Go to next step.
8	INSPECT EGR VALVE PASSAGE Turn the ignition switch off. Remove EGR valve. Is gasket installation normal?	Yes	Go to next step.
8		No	Install gasket correctly, then go to the next step.
9	MONITOR EGR SYSTEM BY DRIVE MODE Clear DTC from PCM memory using. WDS or equivalent. Run PCM adaptive memory procedure drive mode. (See OBD-II DRIVE MODE .) Access RFC FLAG PID using WDS or equivalent. Is RFC FLAG PID OFF?	Yes	Retry this step.
9		No	Go to next step.
10	MONITOR EGR SYSTEM BY DRIVE MODE Run HO2S heater, HO2S, and EGR system repair verification drive mode. (See OBD-II DRIVE MODE .) Check EGR System Monitor is checked using On-Board Readiness Test function. Has EGR system been monitored?	Yes	Go to next step.
10		No	Retry this step.
11	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 ID 10: 31: 83 (EGR flow test) value. Is value within specification?	Yes	Go to next step.
11		No	Replace PCM, then go to next step.
12	VERIFY AFTER REPAIR PROCEDURE Perform "After Repair Procedure". (See AFTER REPAIR PROCEDURE .) Is there any DTC present?	Yes	Go to applicable DTC inspection. (See DTC TABLE .)
12		No	Troubleshooting completed.