O2 sensors are found on nearly all vehicles. Since the early 1980s, in fact, they've been required on all vehicles in the United States. O2 sensors, of course, are designed to detect oxygen. They measure oxygen levels while subsequently sending this information to the vehicle's engine control unit (ECM). While they are fairly simple, however, there are several O2 sensor myths you should ignore.
#1) You Can Always Diagnose a Bad O2 Sensor With CEL
Some drivers assume that they can always diagnose a bad O2 sensor with their vehicle's Check Engine Light (CEL). If the CEL illuminates, it may indicate a bad O2 sensor. You can use an OBD-II scanner to find the code that triggered the CEL. While the CEL code may indicate a problem with the oxygen, it doesn't necessarily mean that your vehicle has a bad O2 sensor. CEL codes only reveal symptoms of a problem; they don't reveal the underlying cause.
#2) Vehicles Only Have One O2 Sensor
In the past, many vehicles only had a single O2 sensor, but this is no longer the case. Most new vehicles now have multiple O2 sensors. Your vehicle have may have an O2 sensor before the catalytic converter, followed by another O2 sensor immediately after the catalytic converter. If you have a dual-exhaust system, conversely, your vehicle may have a total of four O2 sensors.
#3) Only Affects Emissions
O2 sensors certainly affect emissions, which is why they are now required in all vehicles in the United States. But they can still affect engine performance. O2 sensors work in conjunction with the ECM to control the ratio of fuel to air. If an O2 sensor fails, your vehicle's engine may burn too much fuel and too little air, or it may burn too much air and too little fuel. Regardless, it will harm the performance of your vehicle's engine.
#4) Difficult to Replace
Unless you've done it in the past, you may assume that O2 sensors are difficult to replace. After all, they are located around the catalytic converter. You'll have to get underneath your vehicle to access the O2 sensors. But replacing them is easier than you may think. With just a few basic tools, including a wrench, you can replace them yourself.
#5) They Never Go Bad
O2 sensors can absolutely go bad. Under normal circumstances, most of them will last for up to five years. Regular use, though, can cause them to fail. Failure will prevent the O2 sensor from accurately sensing oxygen levels in the exhaust system.