Oxygen Sensor Types

Oxygen sensors provide information to the engine computer used to adjust the fuel mixture for efficient engine operation. There are two basic types of oxygen sensors and the sensors are used in two locations in many vehicles.

Unheated

Oxygen sensors create their own electricity, but must be hot to do so. Older oxygen sensors are unheated, relying on heat from the engine exhaust to warm the sensor. Unheated oxygen sensors are easily identified as they have one or two wires connected to the sensor.

Heated

Automobiles started using heated oxygen sensors in the 1990s; these oxygen sensors have an electrical heating element to warm the sensor. The advantage of heated oxygen sensors is they operate more quickly at startup than unheated sensors. Heated sensors have three or four wires connected to the sensor, with the added wires being used to operate the heating element.

Front and Rear

Vehicles manufactured from the mid-1990s have oxygen sensors located in the exhaust system above and below the catalytic converter. The two oxygen sensors are used to determine changes in the exhaust gases after they have passed through the converter. If the system does not note a change, a dashboard light will indicate a problem to the driver.