DTC P0401 [AJ] (VIN: JM0 LW10J300 301406-, JMZ LW69J7*# 307683-, JM8 LW28J**# 301514-, JM8 LW28A**# 301514- (Assumed))

BME010200400W03

DTC P0401

EGR flow insufficient detected

DETECTION CONDITION

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

POSSIBLE CAUSE

• EGR valve malfunction
• EGR boost sensor malfunction
• EGR boost sensor solenoid valve malfunction
• EGR gasket malfunction
• PCM malfunction

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.
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.
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.
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.
No
Go to next step.
5
INSPECT EGR VALVE MALFUNCTION
• Perform EGR valve inspection.
• Is EGR valve normal?
Yes
Go to next step.
No
Replace EGR valve, then go to Step 9.
6
INSPECT EGR BOOST SENSOR MALFUNCTION
• Perform EGR boost sensor inspection.
• Is EGR valve normal?
Yes
Go to next step.
No
Replace EGR boost sensor, then go to Step 9.
7
INSPECT EGR BOOST SENSOR SOLENOID VALVE
• Perform EGR boost sensor solenoid valve inspection.
• Is EGR valve normal?
Yes
Replace EGR boost sensor solenoid valve, then go to Step 9.
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.
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.
• Access RFC FLAG PID using WDS or equivalent.
• Is RFC FLAG PID OFF?
Yes
Retry this step.
No
Go to next step.
10
MONITOR EGR SYSTEM BY DRIVE MODE
• Run HO2S heater, HO2S, and EGR system repair verification drive mode.
• Check EGR System Monitor is checked using On-Board Readiness Test function.
• Has EGR system been monitored?
Yes
Go to next step.
No
Retry this step.
11
VERIFY TROUBLESHOOTING OF DTC P0401 COMPLETED
• Make sure to reconnect all disconnected connectors.
• Access DIAGNOSTIC MONITORING TEST RESULTS.
• Verify TEST ID 10:31:83 (EGR flow test) value.
• Is value within specification?
Yes
Go to next step.
No
Replace PCM, then go to next step.
12
VERIFY AFTER REPAIR PROCEDURE
• Perform "After Repair Procedure".
• Is there any DTC present?
Yes
Go to applicable DTC inspection.
No
Troubleshooting completed.