Oxygen (O2S) Sensor

O2S is mounted in exhaust manifold or exhaust pipe in front of 3-way catalytic converter. O2S generates voltage according to oxygen content in exhaust gases. Voltage will vary from .1 volts (lean condition) to as high as .9 volts (rich condition).

Sensor will not generate a voltage signal until it reaches an operating temperature greater than 600°F (316°C). Sensor sends voltage signal to ECM, which uses it to obtain correct emissions by adjusting air/fuel ratio. Until sensor is warmed up, ECM adjusts air/fuel mixture based upon preprogrammed ECM memory (Open Loop Operation).