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HOMESERVICE MANUALSMAZDA20086 S SPORT, 4D HATCHBACK, STANDARDREPAIR AND DIAGNOSISEXTERNAL PAGESDIFFERENT CARSECTION 330 (ON-BOARD DIAGNOSTIC (ENGINE CONTROL SYSTEM (L3))DTC P0401DIAGNOSTIC PROCEDURE
2008 Mazda 6 s Sport, 4D Hatchback, Standard

Diagnostic procedure

2008 Mazda 6 s Sport, 4D Hatchback, StandardSECTION Diagnostic procedure
WARNING: This page is about a different car, the 2005 Mazda 6. However, it is still accessible from the selected car via links, so may be relevant.
DTC P0401 [L3] 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 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.
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.
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.
No Go to the next step.
5 INSPECT EGR VALVE MALFUNCTION 
 Yes Go to the next step.
No Replace EGR valve, then go to Step 8.
6 INSPECT MAP SENSOR MALFUNCTION 
 Yes Go to the next step.
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.
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 MODEL 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.
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.
No Retry this step.
10 VERIFY TROUBLESHOOTING OF DTC P0401 COMPLETED 
 Yes Go to the next step.
No Replace PCM, then go to the next step.
11 VERIFY AFTER REPAIR PROCEDURE 
 Yes Go to the applicable DTC inspection. (See DTC TABLE .)
No Troubleshooting completed.
RENDER: 1.0x

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When to See a Mechanic

Stop DIY work and contact a certified mechanic immediately if any of the following apply:

  • • You smell fuel, burning insulation, or see smoke.
  • • Brakes feel soft, pull hard to one side, or make grinding noises.
  • • The engine overheats, stalls repeatedly, or misfires under load.
  • • You are missing required tools, torque specs, or safe lifting equipment.
  • • You are not confident in the next step or safety outcome.