Heated Oxygen Sensor (HO2S)

HO2S is mounted in the exhaust manifold, where it comes in contact with exhaust gases as they enter the exhaust system. HO2S generates voltage according to the oxygen content of exhaust gases. This voltage will vary from .1 volt (lean condition) to as high as 1.0 volt (rich condition). Sensor is electrically heated to reach operating temperature as fast as possible. If sensor is cold or malfunctioning engine will operate in open loop.