Closed Loop

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