What is a Wideband sensor?Standard "narrow band" O2 sensors operate between 0 and 1 volts, and are only capable of accurately measuring a stoichiometric air/fuel ratio (e.g. 14.7:1). A richer or leaner condition results in an abrupt voltage change (see Fig 1.) and thus is only useful for qualitative determination. Modern automobiles use this "switch" like sensing at idle and part throttle to make small compensations in fuel delivery to keep the air/fuel ratio near 14.7:1.
Wide band oxygen sensors utilize a more sophisticated sensing element which enable it to produce precise voltage output in proportion to the oxygen in the exhaust (see Fig 2.) As a result a wide band sensor can measure accurately from as rich as 9.0:1 to as lean as free air. Wide band sensors used to be cost prohibitive, however recently their wide spread use has resulted in lower prices.
Wide band oxygen sensors utilize a more sophisticated sensing element which enable it to produce precise voltage output in proportion to the oxygen in the exhaust (see Fig 2.) As a result a wide band sensor can measure accurately from as rich as 9.0:1 to as lean as free air. Wide band sensors used to be cost prohibitive, however recently their wide spread use has resulted in lower prices. 
Oxygen sensors, or O2 sensors, are required to perform a critical function on your vehicle in the harshest of environments: Measuring the oxygen content of the exhaust just after it leaves the cylinders. The oxygen sensor has to accurately check this red-hot exhaust hundreds of times per minute and send that data to the vehicle computer. The fuel/air mixture hangs in the balance, and you're probably familiar with the symptoms of a bad oxygen sensor: Black smoke from the exhaust, a rotten-egg odor, and poor performance and fuel mileage. 
