Engine Control Module: Description and Operation

The 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 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 in the memory. The diagnostic trouble code tells which circuit the trouble is in. To read diagnostic trouble code from the ECM, use the data link connector.