Introduction

The ECM (ECCS control module) has an on board diagnostic system, which detects engine system malfunctions related to engine sensors or actuators. The ECM also has various emission-related diagnostic information including:
- Diagnostic Trouble Code (DTC) Mode 3 of SAE J 1979
- Freeze Frame data Mode 2 of SAE J 1979
- System Readiness Test (SRT) code Mode 1 of SAE J 1979
- 1st Trip Diagnostic Trouble Code (1st Trip DTC) Mode 7 of SAE J 1979
- 1st Trip Freeze Frame data
- Test values and Test limits Mode 6 of SAE J 1979
These data can be checked using procedures listed in the table below. The malfunction indicator lamp (MIL) on the instrument panel lights up when the same malfunction is detected in two consecutive trips (Two trip detection logic), or when the ECM enters fail-safe mode.