The role of the oxygen sensor is to monitor the amount of oxygen in the exhaust. This is unburnt oxygen that was initially injected into the fuel for proper combustion. Through a voltage signal, the O2 sensor communicates to the car’s computer how much oxygen is in the exhaust, so that the computer can adjust the fuel/oxygen mixture delivered to the engine. The sensor placement before and after the catalytic converter allows it to keep track of the cleanliness of the exhaust, as well as monitor the efficiency of the converter.
Why an Oxygen Sensor May Go BadThe oxygen sensor in modern cars can last up to 100K miles, but typically you would experience problems sooner than that. Over time, an oxygen sensor may become caked with byproducts of combustion, such as sulfur, lead, fuel additives, oil ash, etc. This contamination causes the sensor to lose its ability to produce voltage and send the right signal.
Using fuel that is not recommended for your vehicle or using low-quality gasoline may also speed up the oxygen sensor failure. And if you are skipping maintenance, especially things like timely spark plug and air filter replacement, you are increasing the likelihood of incomplete fuel combustion, which in turn leads to more dirt and grime in your emissions system.
Signs of a Bad Oxygen SensorIn most cases, a bad oxygen sensor will trigger a check engine light. P0138 and P0135 are some of the codes you may expect to see on the OBD II reader if you have one. Other than that, it’s difficult to spot a failing oxygen sensor. It will inevitably lead to decreased gas mileage, but it’s usually not drastic enough for an average driver to notice. The decrease is gradual and happens over time, so unless you are keeping tabs on your MPGs, you will likely miss these signs. A bad or failing O2 sensor can also cause you to fail your emissions test.
Is it Expensive to Replace an Oxygen Sensor?It will typically cost you between $75 and $225 dollars to replace a single oxygen sensor. Most of it is the cost of the sensor itself, which can run anywhere from $30 to $120 depending on the year, make and model of your car. The cost of labor will depend on how accessible the sensor is in your specific vehicle. In some cases, a bad oxygen sensor may indicate other problems, such as a failing catalytic converter, in which case the repair can get expensive.
Replacing a Bad Oxygen SensorReplacing an oxygen sensor is a relatively simple process, but it’s not a DIY job unless you have a lift and have done auto maintenance before. The sensor is located on the underside of your vehicle and may be hard to reach depending on how your vehicle was built. Besides, you would need to have an OBD II reader to know exactly which sensor to replace. If this sounds like too much trouble, just bring your car to Peters Creek Automotive in Roanoke VA, Columbia, Our expert technicians will be able to diagnose.