Oxygen Sensor: Description and Operation

Lambda (Oxygen) Sensor:

PURPOSE
Oxygen sensor voltage signal is translated by ECU as exhaust gas oxygen content. With this measurement, the ECU calculates air/fuel ratio. By comparing oxygen sensor signal with what it "knows" air/fuel ratio should be at any given moment, the ECU can make virtually instantaneous adjustments throughout engine operating range.

OPERATION
Oxygen (Lambda) sensors generate voltage according to exhaust gas oxygen content. The voltage range is approximately 0.1-1.0V. Voltage increases when oxygen content is low (rich) and decreases when oxygen content is high (lean). The ECU determines air/fuel ratio based on voltage generated and makes appropriate adjustments to maintain the optimum 14.7:1 ratio. The difference in oxygen concentration changes greatly in the area of optimum air/fuel ratio, resulting in large voltage changes that are easily calculated by the ECU.

CONSTRUCTION
Sensors incorporate a platinum coated ceramic zirconia tube which generates voltage if there is a difference in oxygen concentration between the inside and outside of the tube.

To operate at peak efficiency, sensors must heat up to approximately 572 - 752°F (300 - 400°C). A heating element, energized by the fuel pump relay, is incorporated into each sensor to facilitate rapid attainment of operating temperature. This system also prevents sensors from cooling down during certain operating conditions such as periods of extended idle.

LOCATION
Exhaust downpipe just below exhaust manifolds.