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Home >> Mazda >> 2003 >> MX-5 Miata Base, Standard >> Repair and Diagnosis >> Engine Performance >> System >> Engine Controls - Self-Diagnostics >> Diagnostic Tests >> DTC P0401: Exhaust Gas RECIRCULATION System Insufficient Flow Detected >> Diagnostic Procedure
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Diagnostic Procedure

  1. Verify Related Repair Information Availability -  Turn ignition off. Connect scan tool to DLC-2. See Figure. Turn ignition on. Monitor for FREEZE FRAME DATA and ensure data has been recorded. Check service bulletins for repair information related to this DTC. If repair information is not available, go to next step. If repair information is available, perform diagnosis and repair as necessary. After repair, go to step  8.
  2. Inspect For Other DTCs -  Leave ignition on. Monitor for other DTCs. If malfunction code recordedis P0401, go to next step. If malfunction code recordedis different than P0401, follow appropriate DTC diagnostic procedure. See DIAGNOSTIC TROUBLE CODE DEFINITIONS .
  3. Inspect Vacuum Hose Condition -  Turn ignition off. Inspect EGR system vacuum hoses for clogs, damage, freezing, or vacuum leaks. If all vacuum hoses are okay, go to next step. If any vacuum hose is faulty repair or replace as necessary. After repair, go to step  8.
  4. Inspect EGR Valve Malfunction -  Perform EGR valve inspection. See EXHAUST GAS RECIRCULATION SYSTEM under EMISSION SYSTEMS & SUB-SYSTEMS in SYSTEM & COMPONENT TESTING - MAZDA6, MIATA, MPV, PROTEGE & PROTEGE5 article. If EGR valve is okay, go to next step. If EGR valve is faulty, replace EGR valve. After repair, go to step  8.
  5. Inspect EGR Boost Sensor Malfunction -  Perform EGR boost sensor inspection. See EXHAUST GAS RECIRCULATION SYSTEM under EMISSION SYSTEMS & SUB-SYSTEMS in SYSTEM & COMPONENT TESTING - MAZDA6, MIATA, MPV, PROTEGE & PROTEGE5 article. If EGR boost sensor is okay, go to next step. If EGR boost sensor is faulty, replace EGR boost sensor. After repair, go to step  8.
  6. Inspect EGR Boost Sensor Solenoid Valve -  Perform EGR boost sensor solenoid valve inspection. See EXHAUST GAS RECIRCULATION SYSTEM under EMISSION SYSTEMS & SUB-SYSTEMS in SYSTEM & COMPONENT TESTING - MAZDA6, MIATA, MPV, PROTEGE & PROTEGE5 article. If EGR boost solenoid valve is okay, go to next step. If EGR boost solenoid valve is faulty, replace EGR boost sensor solenoid valve. After repair, go to step  8.
  7. Inspect EGR Valve Passage -  Turn ignition off. Remove EGR valve, inspect valve passage for clog, blockage and proper gasket installation. If EGR valve passage is okay and gasket is properly installed, go to next step. If EGR valve passage is plugged or gasket is not install properly, repair or replace components as necessary. After repair, go to step  8.
  8. Monitor EGR System By Drive Mode -  Using scan tool, run MODE 1 and 2. See DRIVE MODES  under SELF-DIAGNOSTIC SYSTEM. Check EGR System Monitor completion status using On Board Readiness Test function. If EGR system has been monitored, go to next step. If EGR system has not been monitored, repeat this procedure.
  9. Verify Troubleshooting Of DTC P0401 Completed -  Return vehicle to original condition. Using scan tool, clear DTCs from PCM memory. See CLEARING DIAGNOSTIC TROUBLE CODES  under SELF-DIAGNOSTIC SYSTEM. Access DIAGNOSTIC MONITORING TEST RESULTS of generic OBD-II functions and verify TEST ID 10:41:00 value is within specification, if value is within specification, monitor for DTCs. If same DTC is not present, go to next step. If same DTC P0401 is present, replace PCM. For PCM removal and installation, see POWERTRAIN CONTROL MODULE under COMPUTERIZED ENGINE CONTROLS in REMOVAL, OVERHAUL & INSTALLATION article. After repair, go to next step.
  10. Verify After Repair Procedure -  Using scan tool, perform After Repair Procedure. See AFTER REPAIR PROCEDURE . If no other DTCs are present, testing is complete. If any other DTC is present, go to applicable test and repair.
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