Introduction

The ECM (ECCS control module) has an on board diagnostic system, which detects malfunctions related to sensors or actuators.

The ECM also records various emission-related diagnostic information including:

Diagnostic Trouble Code (DTC) Mode 3 of SAE J1979
Freeze Frame Data Mode 2 of SAE J1979
System Readiness Test (SRT) Code Mode 1 of SAE J1979
1st Trip Diagnostic Trouble Code (1st Trip DTC) Mode 7 of SAE J1979
1st Trip Freeze Frame data
Test values and Test limits Mode 6 of SAE J1979

The above information 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.