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Home >> Mazda >> 2002 >> MX-5 Miata Base, Automatic >> Repair and Diagnosis >> Engine Performance >> System >> Engine Controls - Self-Diagnostics >> Diagnostic Tests >> DTC P0401: Exhaust Gas RECIRCULATION System Insufficient Flow Detected >> Diagnostic Procedure

Diagnostic Procedure

  1. Turn ignition off. Connect New Generation Star (NGS) tester or equivalent to OBD-II Data Link Connector-2 (DLC-2). See Figure. Turn ignition on. Monitor for FREEZE FRAME DATA and ensure data has been recorded. Check for service bulletins and/or other line of repair information related to this DTC. If repair information is available, perform diagnosis and repair as necessary. After repair, go to step  9. If repair information is not available, go to next step.
  2. Leave ignition on. Monitor for other DTCs. If malfunction code recordedis P0401, go to next step. If malfunction code recordedis different that P0401, follow appropriate DTC diagnostic procedure.
  3. 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  9.
  4. Perform a EGR valve inspection. See EGR VALVE - MIATA under EXHAUST GAS RECIRCULATION SYSTEM in SYSTEM & COMPONENT TESTING - MIATA, MILLENIA, MPV, PROTEGE, PROTEGE5 & 626 article. If EGR valve is okay, go to next step. If EGR valve is faulty, replace EGR valve. After repair, go to step  9.
  5. Perform a EGR boost sensor inspection. See EGR BOOST SENSOR - MIATA under EXHAUST GAS RECIRCULATION SYSTEM in SYSTEM & COMPONENT TESTING - MIATA, MILLENIA, MPV, PROTEGE, PROTEGE5 & 626 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  9.
  6. Perform a EGR boost sensor solenoid valve inspection. See EGR BOOST SENSOR SOLENOID VALVE under EXHAUST GAS RECIRCULATION SYSTEM in SYSTEM & COMPONENT TESTING - MIATA, MILLENIA, MPV, PROTEGE, PROTEGE5 & 626 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  9.
  7. 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 faulty and gasket is not install properly, repair or replace components as necessary. After repair, go to step  9.
  8. Using NGS tester or equivalent, 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 step procedure.
  9. Return vehicle to original condition. Using NGS tester or equivalent, clear DTCs from PCM memory. 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 P0401 is present, replace PCM. For PCM removal and installation, see POWERTRAIN CONTROL MODULE under COMPUTERIZED ENGINE CONTROLS in REMOVAL, OVERHAUL & INSTALLATION article. If any other DTC is present, follow appropriate DTC diagnostic procedure.
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