An
Oxygen Sensor, or
Lambda Sensor, is an electronic device that measures the proportion of Oxygen (O2) in the gas or liquid being analyzed. The original sensing element is made with a thimble-shaped zirconia ceramic coated on both the exhaust and reference sides with a thin layer of platinum and comes in both heated and unheated forms. Car
Oxygen/Lambda Sensors, colloquially known as O2 Sensors, make modern electronic fuel injection and emission control possible.
Oxygen/Lambda Sensors determine if the air fuel ratio exiting a gas-combustion engine is rich or lean. Closed-loop feedback-controlled fuel injection varies the fuel injector output according to real-time sensor data rather than operating with a predetermined fuel map. In addition to improving overall engine operation,
Oxygen/Lambda Sensors reduce the amounts of both unburnt fuel and oxides of nitrogen from entering the atmosphere. Information on oxygen concentration is sent to the engine management computer or ECU, which adjusts the mixture to give the engine the best possible fuel economy and lowest possible exhaust emissions. Failure of these sensors, either through normal aging, the use of leaded fuels, or fuel contamination with silicones or silicates, for example, can lead to damage of a vehicle’s catalytic converter and in turn incur expensive repairs. The
Oxygen/Lambda Sensor is typically screwed into a threaded hole in the exhaust system, located after the branch manifold of the exhaust system combines, and before the catalytic converter. Normally, the lifetime of an unheated
Oxygen/Lambda Sensor is about 30,000 to 50,000 miles. Heated
Oxygen/Lambda Sensor lifetime is typically 100,000 miles. Failure of an unheated
Oxygen/Lambda Sensor is usually caused by the buildup of soot on the ceramic element, which lengthens its response time and may cause total loss of ability to sense oxygen. For heated
Oxygen/Lambda Sensors, normal deposits are burned off during operation and failure occurs due to catalyst depletion, similar to the reason a battery stops producing current. The
Oxygen/Lambda Sensor then tends to report lean mixture, the ECU enriches the mixture, the exhaust gets rich with carbon monoxide and hydrocarbons, and the mileage worsens.