Engine Control Module: Description and Operation

Engine Control Module (ECM):

The ECM is mounted to the intake manifold on the front side of the engine beneath the outlet resonator/duct assembly. The ECM uses one main microprocessor to control the engine. The main function of the ECM is to control fuel and spark to the engine. The ECM also controls:
^ A/C relay
^ Cooling fan relay
^ Cruise control
^ Generator L-terminal voltage (needed for charging)

The ECM sends messages to the BCM over the CAN bus to control the:
^ Coolant temp gauge
^ Fuel gauge
^ Change Oil Soon telltale
^ Charge telltale
^ Coolant Temperature telltale
^ Low Fuel telltale
^ Malfunction Indicator Lamp (MIL)
^ Oil Pressure telltale
^ Service telltale
^ Speedometer
^ Tachometer
^ Upshift telltale

The ECM uses inputs from various sensors, processes the information and commands output devices. It performs diagnostics on both input and output circuits that have associated Diagnostic Trouble Codes (DTCs). If a circuit fault exists when certain DTC parameters have been met, a DTC will be set and the ECM will store Freeze Frame/Failure Record information.