Electronic Control Module: Notes

The ECM controls all functions of the closed loop system. The ECM sends an electrical signal to the vacuum control or M/C solenoid which controls the air/fuel mixture by vacuum signals. This control signal is constantly cycling the solenoid between "ON" and "OFF" time (duty cycle) as a function of the input voltages from the data sensors.

The control signal generated by the ECM is selected from 4 operational modes. These modes include: Inhibit Mode, Enrichment Mode, Open Loop Mode and Closed Loop Mode. A brief description of each mode is as follows: