Operation

When exhaust oxygen content is high, oxygen sensor voltage output is low. When exhaust oxygen content is low, oxygen sensor voltage output is high. The greater the difference in oxygen content between the exhaust stream and atmosphere, the higher the voltage signal.

Exhaust Oxygen Content

Oxygen Sensor Output

Air/Fuel Ratio Judged To Be

Low —— "T—

I»- High, Above 0.45 volts

High in Illi

► Low, Below 0.45 volts

-

From the oxygen content, the ECM can determine if the air/fuel ratio is rich or lean and adjusts the fuel mixture accordingly. A rich mixture consumes nearly all the oxygen, so the voltage signal is high, in the range of 0.6 - 1.0 volts. A lean mixture has more available oxygen after combustion than a rich mixture, so the voltage signal is low, 0.4 - 0.1 volts. At the stoichiometric air/fuel ratio (14.7: 1), oxygen sensor voltage output is approximately 0.45 volts.

Oxygen Sensor Voltage Range

ECM Cannot Tell How Rich

ECM Cannot Tell How Lean

The oxygen sensor is unable to detect how rich or lean the air/fuel mixture is.

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