Run Mode

The Run Mode has two conditions, called "Open Loop" and "Closed Loop." When engine is first started and rpm is above 400 rpm, system goes into "Open Loop" operation. In "Open Loop", PCM ignores signal from Oxygen (O2) sensor, and calculates air/fuel ratio based on inputs from Coolant and MAP sensors.

The system will stay in "Open Loop" until the following conditions are met:

1. The O2 sensor has varying voltage output, showing that it is hot enough to operate properly (This depends on temperature.)
2. The Coolant Sensor is above 58°C.
3. A calibrated (about 60 seconds) time delay has elapsed after starting engine. This delay allows all sensors to stabilize.

When these conditions have been satisfied, system goes into CLOSED LOOP operation. In CLOSED LOOP, PCM will calculate air/fuel ratio (injector on-time) based on signal from O2 sensors. This allows air/fuel ratio to stay very close to 14.7:1.