Oxygen (O2) Sensor
The O2 sensor of your vehicle records the temperature and amount of oxygen inside your vehicle’s exhaust system. Using a series of voltage signals and your engine’s computer, the O2 sensor compares the exhaust steam temperature to the temperature of the surrounding air. Your engine uses these temperature and oxygen readings to take in the optimal amount of fuel while driving. It can also trigger the check engine light to alert you of emissions issues. The O2 sensor is just one of many different sensors that your engine relies on to optimize the air to fuel ratio in your engine.
There are two types of O2 sensors: upstream and downstream. Your vehicle likely has both and depending on the model of car may have multiple of one or both types.
Upstream sensor
Your upstream O2 sensor is mounted very closely to the engine, before the catalytic converter. The engine computer utilizes the readings from this sensor for fuel control. If the sensor detects a lean condition (when there is too much oxygen in the mix) more gasoline will be added to the engine. When the sensor detects a rich condition (too little oxygen in the mix) fuel sent to the engine is reduced.
Downstream sensor
Your downstream O2 sensor is mounted after the catalytic converter, further away from the engine. It ensures that your catalytic converter is working efficiently and creating clean exhaust.
Newer vehicles have been making use of a third kind of O2 sensor known as a wide-band upstream oxygen sensor. You can think of these types of O2 sensors as “smart” O2 sensors that are able to make air to fuel ratio adjustments more easily.
Signs of a bad oxygen (O2) sensor
- Check engine light illuminates – When the check engine light turns on as a result of an O2 sensor issue, it is due to either the sensor signal being out of range because of an engine issue or because the sensor has stopped working. The trouble code will tell your technician exactly what the issue is so that they can resolve the problem from there.
- Poor fuel economy – A faulty O2 sensor can cause the computer to deliver too much fuel to the engine, causing poor fuel economy.
- Poor engine performance – Engine misfires, stalling, and overall rough running can all be the result of an O2 sensor going bad.
Oxygen (O2) sensor maintenance
O2 sensors will often fail as a result of fluid contamination from a leak. If this is the case, your technician will fix the leak first before replacing the O2 sensor. All faulty O2 sensors should be replaced to ensure good engine and exhaust performance.
The best way to get your O2 sensor serviced is by booking your appointment through CarAdvise. CarAdvise makes car care simple and guarantees that you’ll pay less than the retail shop price on all car maintenance services.
« Back to Glossary Index