General System Description

SYSTEM DESCRIPTION

The engine, in this vehicle, uses an Engine Control Module (ECM) to assist in reducing exhaust emissions and maintaining good fuel economy. The computer has approximately 20 input sensors used to gather various information. The vehicle contains a Body Control Module (BCM) which controls various vehicle functions based on data sensors and input switches.

The BCM and ECM systems have a built-in diagnostic system that recognizes and identifies possible operational problems, and signals the driver through an "ENGINE CONTROL SYSTEM FAULT" Light located on the instrument panel. The dash-mounted control system light is used to inform the technician of a system malfunction. The ECM stores a trouble code associated with the detected failure until the codes are cleared or 50 ignition switch (on-off) cycles have occured without any fault.

The system stores two types of trouble codes. The Current Code is a malfunction which has recently occurred, and the "Engine Control System Fault" light is on as long as the malfunction is present. The History Code is an intermittent malfunction which has occurred within the last 50 ignition cycles. History codes will be designated with the word "HISTORY" after the code number has been displayed. Recent codes will have the word "CURRENT" after the code number has been displayed.