Oxygen Sensor FAQ’s -- West Automotive Group
Your car has something called an oxygen sensor. You may have also discovered that if an oxygen sensor goes bad, it can trigger a check engine warning. But perhaps you still have some additional questions about the O2 sensor. We'll be glad to answer the most frequently asked questions for you. When you're ready for service or repair, we're here for that, too. Since 1993, West Automotive Group in Miramar, California, has built a reputation for outstanding automotive and customer service. Our ASE and ATRA certified technicians look forward to assisting you whether you need oxygen sensor replacement, an oil change, or a transmission overhaul.
What is it?
An oxygen sensor measures the amount of unburned oxygen that is left over after combustion. It does this by checking the amount of oxygen that exits your vehicle through the exhaust, relaying that information to the computer. Your auto uses this reading to determine whether the fuel to air ratio is appropriate. If there is too little oxygen, the engine is said to be running "rich." Too much oxygen constitutes the description of running "lean." The computer adjusts the ratio to ensure that your car runs optimally. In reality, unless you drive an older auto, you have more than one oxygen sensor.
Why is it there?
Not only do oxygen sensors help your vehicle run efficiently, but they’re also required to be there. All cars made since 1981 have one. When the universal OBD-II system became mandatory in 1996, a second oxygen sensor was required. It's located below the catalytic converter. The second reading it provides checks the catalytic converter for proper function. The second sensor, which measures exhaust fumes after they have passed through the catalytic converter, should show a lower reading than the first sensor. This means that the catalytic converter is working. If there is little change between the two measurements, the catalytic converter isn't doing what it was designed to do. Depending upon the make or model you drive, your auto may have as many as four O2 sensors. Larger engines (V-6 or V-8) sometimes have one located in each cylinder row and another after each catalytic converter. (Note: Most autos have a single catalytic converter. However, some dual exhaust--two tailpipes--cars have one for each side.)
How will you know if it needs replacing?
If one of the oxygen sensors goes bad, you may experience noticeable engine problems. These include rough idling, stalling, an increase in fuel use, misfiring spark plugs, or a lack of power. The check engine light will likely illuminate, too. If any of this occurs, bring your vehicle to West Automotive Group in Miramar, California, where technicians can check it with an OBD-II reader and determine if you need an oxygen sensor.
