On-Board Diagnostic [Engine Control System L3): Foreword

When the customer reports a vehicle malfunction, check the malfunction indicator lamp (MIL) indication and diagnostic trouble code (DTC), then diagnose the malfunction according to following flowchart.
- If the DTC exists, diagnose the applicable DTC inspection. (See DTC TABLE ).
- If the DTC does not exist and the MIL does not illuminate or flash, diagnose the applicable symptom troubleshooting. (See QUICK DIAGNOSTIC CHART ).
  
  Fig 1: Symptom Troubleshooting Flow Chart
  Courtesy of MAZDA MOTORS CORP.