Oxygen Sensor: Description and Operation

DESCRIPTION
There are four Heated Oxygen Sensors (HO2S):
- two are located in the exhaust pipes below the exhaust manifold before the catalytic converters.
- two are used as catalyst monitors behind the catalytic converters.
- these sensors react with the oxygen in the exhaust gases and generate a voltage based on this reaction.
- a low voltage indicates too much oxygen or a lean condition.
- a high voltage indicates not enough oxygen or a rich condition.