Oxygen Sensor Replacement

Did you know replacing worn or failed oxygen sensors can protect your expensive catalytic converters? Failure to replace faulty oxygen sensors at the earliest sign of a problem, usually indicated by the check engine light and associated trouble code, can cause premature failure of expensive catalytic converters.

When an oxygen sensor fails, it is no longer providing the correct signal to the vehicle’s Engine Control Unit (ECU). The ECU is responsible for controlling the fuel delivery thru the fuel injectors in “closed-loop” mode to maintain the correct air-fuel ratio of 14.7 parts air to 1 part fuel (14.7:1), also known as the stoichiometric point. When there is a faulty signal, or lack of signal from an oxygen sensor, the ECU will control the fuel delivery in “open-loop” mode, in which a programmed amount of fuel (usually richer) is delivered to protect the engine from damage by an over-lean condition. Running in open-loop mode will not only waste fuel and increase emissions, it decreases the longevity of numerous components, one being the catalytic converter.

The catalytic converter contains expensive precious metals such as platinum, rhodium and palladium to create chemical reactions that convert harmful gases: carbon monoxide (CO), nitrogen oxide (mainly NOx) and hydrocarbons (HC) to less harmful gases such as carbon dioxide (CO2), nitrogen (N), oxygen (O2) and water (H2O) vapor.

When the vehicle is operating in open-loop mode, the engine can run rich, resulting in higher levels of unburned fuel. Excess unburned fuel can cause elevated temperatures and eventually lead to a melted/destroyed catalytic converter. Vehicle performance can further degrade if the converter becomes plugged – and the engine might even fail to run. Replacing a failed oxygen sensor at the earliest sign of trouble may save future headaches and higher repair bills