Have you ever taken your car to a shop to diagnose a Check Engine light, and an hour later the mechanic comes out and confidently declares that you have a bad O2 sensor? For many car owners, the word "sensor" means easy, not important, or something very simple. But have you ever wondered what an O2 sensor actually does? Here is a basic overview of O2 sensors, also known as oxygen sensors.

What O2 Sensors Do

Put simply, O2 sensors help regulate your car engine's air-fuel ratio. Each explosion in your car's combustion chambers is caused by an ignition of air and fuel. When the ratio of air and fuel taken into those chambers remains optimal, your car will run and idle just fine. However, when there is too much fuel taken in, that means the system is running "rich," and your car's performance will suffer. Same thing when there is too little fuel taken in, also known as running "lean".

Because of this, there are at least two O2 sensors installed in your car: the upstream and downstream sensors. They both work basically the same way: they sense the amount of unburned oxygen at different points in the exhaust system, and emit a voltage that corresponds to that amount. The voltage emitted determines the level of fuel taken into the combustion chambers. If your system is running lean, the O2 sensors will signal for more fuel; if it's running rich, they will signal for less. Amazingly, this process is constantly taking place as you drive your car! The main point of all of this is to consistently keep your air-fuel ratio at the optimal level for your car.

Let a Professional Help

The tricky thing with O2 sensors is that when your Check Engine light comes on, your OBD2 codes will indicate that you have a bad O2 sensor, when in reality you don't! The reason for that is simple: many of your car's codes only tell you about the symptoms of the problem, not the actual cause. So before you shell out those hundreds of dollars just replacing parts, make sure your mechanic has thoroughly diagnosed and tested the entire system to pinpoint the true, correct failure and reason for setting off the Check Engine Light. At Christian Brothers Automotive, we have professional, Master Certified ASE technicians, who will not hastily replace parts that are still working, but will work hard to determine the true cause behind that pesky Check Engine light. Please come see us today!