The ECM/PCM is activated by power supply. Signals from several sensors, such as CKPS and APS, is inputted to ECM/PCM. Comparing inputted siganals with control LOGIC are saved at micro controller and EEPROM, the ECM/PCM controls engine as actuating injectors, solenoids and relays.

To guarantee accurate control, the ECM/PCM performs SELF TEST, DIAGNOSIS of several sensors and actuators. If serious trouble which affects vehicle performance occurrs, the ECM/PCM sets DTCs.

At certain cases, the ECM/PCM shuts down whole systems in order to prevent dangerous situation due to incorrect control.