Engine Control Module: Description and Operation

Electronic Control Module (ECM) located under instrument panel, left of steering column, is control center of fuel injection system. It constantly looks at information from various sensors, and controls systems that affect vehicle performance. ECM also performs diagnostic function of system. It can recognize operational problems, alert driver through "Check Engine" light, and store a code or codes which identify problem areas to aid technician in making repairs.

ECM supplies either 5 or 12 volts to power various sensors or switches and controls output circuits such as fuel injectors, IAC valve, A/C clutch relay, etc. by controlling ground circuit through transistors or a "quad-driver".