Engine Control Module Description: Notes

The engine control module (ECM) interacts with many emission related components and systems. The ECM also monitors emission related components, and systems, for deterioration. The on-board diagnostics monitor the system performance and a diagnostic trouble code (DTC) sets if the system performance degrades.

The malfunction indicator lamp (MIL) operation and DTC storage are dictated by the DTC type. DTCs are ranked as a Type A, B or C. Types A and B DTCs are emissions related. A Type C DTC is non-emissions related.

The ECM is the control center of the engine controls system. The ECM controls the following components:

• The fuel injection system
• The ignition system
• The emission control systems
• The on-board diagnostics
• The A/C and fan systems
• The throttle control (TAC) system (if equipped)
• The idle air control (IAC) system (if equipped)
• The idle speed control (ISC) system (if equipped)

The ECM constantly monitors the information from various sensors and other inputs, and controls the systems that affect the vehicle performance and emissions. The ECM also performs diagnostic tests on various parts of the system. The ECM can recognize operational problems and alert the driver via the MIL. When the ECM detects a malfunction, the ECM stores a DTC. The condition area is identified by the particular DTC that is set. This aids the technician in making repairs.