Engine Control Module: Description and Operation

DESCRIPTION
The Engine Control Module (ECM) mainly controls the following items:
- Fuel Control.
The ECM controls the Air/Fuel delivery to the combustion chamber by controlling the fuel flow through the Injector(s).
- Electronic Spark Timing.
This system is controlled by the ECM which controls spark advance (timing).
- Exhaust Gas Recirculation.
This system uses a valve to feed a small amount of exhaust gas back into the Intake Manifold to control formation of Oxides of Nitrogen (NOx).
- Idle Air Control.
The ECM controls the engine idle speed to the desired rpm, for different operating conditions.
- Diagnosis.
If a Sensor reading is not what the ECM thinks it should be, the ECM will turn on the "CHECK ENGINE" light and store a Diagnostic Trouble Code (DTC) in the memory. The DTC tells which circuit the trouble is in. To read a DTC from the ECM, use the Data Link Connector.