Automotive oxygen sensors, also known as lambda sensor or O2 sensors are used in most cars both in the US and in other countries. It is an electronic device which measures the proportion of oxygen (O2) in the gas of an automobile. It was developed by the Robert Bosch GmbH company during the late 1960s under the supervision of Dr. Gunter Bauman. It also makes modern electronic fuel injection and emission control possible. It helps determine if the air fuel ratio of a combustion engine is rich or lean. The sensor does not actually measure oxygen concentration; instead, it measures the amount of oxygen needed to completely oxidize and remaining combustibles in the exhaust gas.
Oxygen sensors, along with catalytic converters are used by modern spark-ignited combustion engines to reduce exhaust emissions. Information on oxygen concentration is sent to the engine management computer, which adjusts the amount of fuel injected into the engine to compensate for excess air or excess fuel. Tampering with or modifying the signal that the oxygen sensor sends to the engine computer can be detrimental to emission control and can even damage the vehicle. Failure of sensors, either through normal aging, the use of leaded fuels, or fuel contaminated with silicones or silicates, can lead to damage of an automobile’s catalytic converter and extensive repairs.
By 1996, all cars have multiple 02 sensors. One is located in between the engine and catalytic converter, while the other is positioned behind the catalytic converter. The engine control module monitors the extra sensor to verify the efficiency of the catalytic converter. With normal operation, this oxygen sensor produces almost no voltage because the catalytic converter consumes everything.
The normal lifetime of an unheated sensor is 30,000 to 50,000 miles (50,000 to 80,000 km), while the lifetime of a heated sensor is typically 100,000 miles (16,000 km). The symptoms of a failing oxygen sensor include:
- Sensor light on dash indicates problem
- Increased tailpipe emissions
- Increased fuel consumption
- Hesitation on acceleration
- Rough idling
When the oxygen sensor fails, the computer can no longer sense the air/fuel ratio, so it ends up guessing. The car performs poorly and uses more fuel than it needs to.