How to Test Your O2 Detector

Your vehicle’s O2 detector is an important part of your car’s emissions control system, and it is constantly measuring the oxygen content inside the exhaust flow as compared to the air outside of the exhaust. It then generates a voltage signal to your engine controller, which alters the fuel mixture accordingly. Your vehicle may have one or two oxygen sensors, depending on its model and powertrain type.

How do I know if it’s my catalytic converter or O2 sensor?

The sensor consists of a ceramic cylinder plated inside and out with porous platinum electrodes. When the hot exhaust gas flows across these electrodes, it dissolves some of the oxygen molecules, generating a voltage. The sensor’s electrodes are positioned so that they measure the difference between the oxygen concentration in the hot exhaust gas and that in the ambient air. Your vehicle uses either conventional zirconia or wide-band oxygen sensors, which use different methods of detection. Conventional zirconia sensors react to rich-lean indicators while wide-band sensors can detect the exact fuel-to-air ratio over a much wider range.

Over time, your o2 sensor will eventually begin to wear out due to contamination or high operating temperatures. It will take longer to produce a voltage signal, which can cause your engine to run sluggishly and increase its fuel usage. A faulty oxygen sensor may also cause the check engine light to illuminate, which could result in your vehicle failing an emissions test.

You can test your o2 sensor using a diagnostic scanner or another electronic device capable of reading oxygen sensor voltages. When the engine is running properly and the fuel mixture is 14.7:1 (stoichiometric), a healthy sensor will generate a low-level voltage of up to 0.9 volts.

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