Engine Control Module: Notes

For exact location of Engine Control Module (ECM), see COMPONENT LOCATIONS in SELF-DIAGNOSTICS - 2.2L ION article. On some models, the ECM may be referred to as an Powertrain Control Module (PCM). Although the 2 units may process different signals, the 2 terms are interchangeable.

The powertrain has electronic controls to reduce exhaust emissions while maintaining excellent driveability and fuel economy. The ECM is the control center of this system. The ECM monitors numerous engine and vehicle functions. The ECM constantly looks at the information from various sensors and other inputs, and controls the systems that affect vehicle performance and emissions. The ECM also performs the diagnostic tests on various parts of the system. The ECM can recognize operational problems and alert the driver with the Malfunction Indicator Light (MIL). When the ECM detects a malfunction, the ECM stores a Diagnostic Trouble Code (DTC). The problem area is identified by the particular DTC that is set. Review the components and wiring diagrams in order to determine which systems are controlled by the ECM. The following are some of the functions that the ECM controls:

• The engine fueling.
• The Ignition Control (IC).
• The Knock Sensor (KS) system.
• The Evaporative Emissions (EVAP) system.
• The generator.
• The A/C clutch control.
• The cooling fan control

The ECM constantly looks at the information from various sensors and other inputs and controls systems that affect vehicle performance and emissions. The ECM also performs diagnostic tests on various parts of the system. See SELF-DIAGNOSTIC SYSTEMS  . The ECM can recognize operational problems and alert the driver with the Malfunction Indicator Light (MIL). When the ECM detects a malfunction, the ECM stores a Diagnostic Trouble Code (DTC). The problem area is identified by the particular DTC that is set. The input and output devices in the ECM include analog-to-digital converters, signal buffers, counters, and output drivers. The output drivers are electronic switches that complete a ground or voltage circuit when turned on. Most ECM controlled components are operated by output drivers. The ECM monitors these driver circuits for proper operation and, in most cases, can set a DTC corresponding to the controlled device if a problem is detected.