Oxygen Sensor: Description and Operation

Fig.14 - Closed Loop Feedback System Oxygen Sensor:

The oxygen sensor, Fig. 14, measures the amount of oxygen present in the exhaust gasses. The sensor reacts to the oxygen and develops a voltage signal which is sent to the electronic control unit. The control unit determines the air/fuel mixture ratio from the signal and controls the fuel regulator accordingly, in order to maintain the correct mixture.

Fig.15 - Vacuum Solenoid Regulator:

When the oxygen sensor registers a rich mixture, it sends a stronger voltage signal to the control unit. A signal from the control unit causes the solenoid core to remain in top (55) position for a greater percentage of time than it remains in the lower (SI), Fig. 15, position. Vacuum to the carburetor actuators increases, causing leaner air/fuel mixtures. When the oxygen sensor registers a lean mixture, it sends a weaker signal to the control unit. The signal from the control unit then causes the solenoid core to spend a greater percentage of time in the lower (SI) position, decreasing vacuum to the carburetor actuators, causing leaner air/fuel mixtures.