Engine Control Module: Description and Operation

PURPOSE
The Engine Control Module (ECM) controls the fuel injection system, ignition timing, and the idle speed control system. The ECM also interrupts the operation of the air conditioning and EGR systems, and controls power to the fuel pump (through the control relay).

OPERATION
Based on information from the input sensors (engine coolant temperature, barometric pressure, air flow, etc.), the ECM determines optimum settings for the output actuators (injection, idle speed, ignition timing, etc.).

SELF-DIAGNOSIS
The ECM constantly monitors input and output signals for correct operating range. If an irregularity occurs, the ECM stores a trouble code which can be accessed via the self-diagnosis output terminal. Diagnostic results can be read with a Voltmeter or Scan Tool.