Wide Band oxygen sensors may also be referred to as 5 Wire oxygen sensors and Air/Fuel sensors (although not all Air/Fuel sensors are wide band).



Simple explanation first.
Wide Band sensors operate different from traditional oxygen sensors by producing a variable voltage based on the air/fuel ratio in the exhaust gas. This is different from earlier oxygen sensors as they only reported if the air/fuel mix was rich or lean, but not how rich or how lean. A Wide Band Oxygen sensor is superior because it helps the ECU maintain a stoichiometric air/fuel mixture by supplying a variable voltage telling the ECU how rich or lean the current exhaust gas is. This allows for far more accurate and efficient engine fuel management.


Extra credit material. (without the technical stuff)
There are significant engineering differences between how the wide band sensor and its predecessor, the zirconia planar sensor operate. However, we are not prepared to go into Nernst cell anode/cathode diffusion gaps, so we’ll keep it simple. The 5 wire or Wide Band oxygen sensor builds upon the original planar design, but it adds the ability to actually measure the air/fuel ratio directly. Instead of only switching back and forth from rich to lean like its binary zirconia predecessor, the wide band oxygen sensor produces a variable (voltage) that tells the ECU how rich or how lean the current air/fuel mixture is. This is a much more precise method of metering the air/fuel mixture. Instead of constantly cycling back and forth from rich to lean to keep up with the latest report from the oxygen sensor, the ECU can now maintain a constant 14.7:1 mixture (also known as stoichiometric) because of the superior reporting from the wide band sensor.

Other differences between the 5 wire wide band oxygen sensor and the zirconia planar type are, the 5 wire wide band operates at about 1200 to 1500° Fahrenheit instead of the standard operational temperature of about 600° (316° Celsius). Also it does not produce its own voltage; it is reliant on a controller or ECU to supply a reference voltage to operate. Based on the oxygen content of the exhaust, the sensor delivers a signal ranging from 5 volts for a rich mixture to 0 volts for an extremely lean mixture (0.0 volts for straight air), A standard zirconia sensor reported a simple binary signal of greater or lesser than 450 millivolts.