Engine Control Module: Description and Operation

The ECM controls the air/fuel ratio by varying the Duty Cycle [1] of the vacuum controller solenoid as a function of sensor input voltages.

ECM Modes Of Operation:

Inhibit Mode - No signal to vacuum controller solenoid.

Enrichment Mode - Fixed pre-programmed duty cycle to vacuum controller solenoid.

Open Loop Mode - Fixed pre-programmed duty cycle to vacuum controller.

Closed Loop Mode - Calculated duty cycle generated from sensor inputs--including oxygen sensor.

[1] Duty Cycle - the percentage of time the solenoid is ON.