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Home >> Mazda >> 2002 >> MX-5 Miata Base, Standard >> Repair and Diagnosis >> Engine Performance >> System >> Engine Controls - Self-Diagnostics >> Diagnostic Tests >> DTC P0103: Mass Airflow Sensor Circuit High Input >> 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  6. If repair information is not available, go to next step.
  2. Start engine. Using New Generation Star (NGS) tester or equivalent, access MAF PID. MAF PID should be on a vehicle equipped with automatic transaxle 0.30-0.41 lb/min (2.2-3.2 g/sec) and with manual transaxle 0.31-0.41 lb/min (2.3-3.2 g/sec). If MAF PID is not as specified, go to next step. If MAF PID is as specified, problem is intermittent, See INTERMITTENTS in TROUBLE SHOOTING - NO CODES article.
  3. Turn ignition off. Disconnect MAF sensor 3-pin harness connector. See Figure. Check for poor connection due to damaged, pulled-out pins, corrosion, etc. If connector terminals are okay, go to next step. If connector terminals are found faulty, repair or replace as necessary and go to step  6.
  4. Leave MAF sensor harness connector disconnected. Turn ignition on. Measure voltage between ground and MAF harness connector terminal "B" (Pink wire). Voltage should be 0.1 volt. If voltage is as specified, go to next step. If voltage is not as specified, repair open or short circuit (in Pink wire) between MAF sensor and PCM. For circuit identification, see MIATA in WIRING DIAGRAMS article. After repair, go to step  6.
  5. Turn ignition off. Leave MAF sensor harness connector disconnected and disconnect PCM 31-pin harness connector. See Figure. Check for poor connection due to damaged, pulled-out pins, corrosion, etc. If connector terminals are okay, go to next step. If connector terminals are found faulty, repair or replace as necessary and go to step  6.
  6. Return vehicle to original condition. Using NGS tester or equivalent, clear DTCs from PCM memory. Start engine and access MAF PID. MAF PID should be on a vehicle equipped with automatic transaxle 0.30-0.41 lb/min (2.2-3.2 g/sec) and with manual transaxle 0.31-0.41 lb/min (2.3-3.2 g/sec). Monitor for DTCs. If same DTC P0103 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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