Closed Loop

The specific values for the above conditions vary with different engines and are stored in the Electronically Erasable Programmable Read-Only Memory (EEPROM). When these conditions are met, the system goes into "Closed Loop" operation. In "Closed Loop," the ECM calculates the air/fuel ratio (fuel injector on-time) based on the signal from the heated oxygen sensor. This allows the air/fuel ratio to stay very close to 14.7:1.