How are oxygen sensors typically tested?

Oxygen sensors are typically tested using millivolts. This is because they generate a small voltage that is proportional to the amount of oxygen in the exhaust gases. The operation of a zirconia oxygen sensor, which is the most common type, relies on a chemical reaction between the oxygen in the exhaust and the oxygen present on one side of the sensor. As the exhaust gas composition changes, the voltage output of the sensor changes correspondingly, allowing the engine control unit (ECU) to determine the air-fuel mixture ratio.

Testing in millivolts provides a high level of sensitivity and accuracy for detecting small changes in the exhaust gas composition, which is crucial for proper engine management and emissions control. Assessing the voltage in this range ensures that technicians can accurately interpret the oxygen sensor's performance and diagnose any issues related to fuel efficiency and emissions control systems.