Most newer engines have multiple oxygen sensors, and the location of each oxygen sensor is identified according to position and cylinder bank, according to AA1 Car. A diagnostic tool has the ability to identify the specific location of sensors experiencing malfunction issues.
Sensors are normally identified as sensor one, two or three. V6 and V8 engines always have sensor one on the same side as the number one cylinder. The number one cylinder refers to the cylinder that fires first when the engine starts. Four- and six-cylinder engines only have one bank of cylinders, which means that all oxygen sensors are located in cylinder bank one, according to AA1 Car.