Prior to the mid 1970s, vehicles lacked oxygen sensors. At the time, few people worried about the emissions coming from their car’s tailpipe. That changed in 1976 when Bosch released the prototype that would eventually become the standard for the automotive industry. The individual states soon began requiring vehicles to be equipped with the component as part of a growing movement to reduce emissions. Today, every vehicle is built with an oxygen sensor (OS).
Few people are aware of how this automotive part works, or its role in the performance of their engine. We’ll address both of these areas below. In this article, we’ll explain the O2 sensor’s function and describe its operation. We’ll also take a look at how it can fail, and what you should do if it does.
Basics Of An Oxygen Sensor’s Function
All cars, trucks, and SUVs are designed with at least one OS. Many vehicles, notably those with eight or ten cylinders, are equipped with two. Some even have four. The component is located within the exhaust manifold, and may be mounted before or after your catalytic converter. Its job is to measure the level of oxygen in the exhaust exiting each cylinder’s combustion chamber. By doing so, it identifies situations in which an excess or deficit of O2 is present.
If a higher-than-normal level exists, it indicates the air-fuel mixture within one or more of the cylinders is too lean. If the level is lower than it should be, the blend is too rich. This information is sent to your car’s powertrain control module (PCM). The PCM uses this data, along with data from other sensors, to adjust the amount of fuel sent to your engine. The blend is thus made more lean or rich to improve the ratio between air and fuel. The resulting exhaust is monitored by the O2 sensor. This represents a closed loop.
The piece of the O2 sensor that monitors the level of oxygen is a small zirconium ceramic bulb. The interior and exterior surfaces of the bulb are covered with platinum. The exhaust makes contact with the bulb and flows inside it through tiny spaces. While the exhaust covers the platinum on the exterior, it also generates a voltage inside the bulb based on the amount of oxygen. When there is too much, the voltage rises. When there is too little, it drops. It is this voltage that is sent to the PCM.
Can The Component Fail?
Over time, contaminants in the exhaust coming from the engine coat the individual pieces of the O2 sensor. They accumulate inside, slowing it down and impairing its ability to correctly measure the level of oxygen. The sensor deteriorates and becomes less capable of generating voltage that accurately reflects the oxygen in the exhaust.
As a result of this deterioration, inaccurate data is sent to the powertrain control module. This prevents the PCM from correctly adjusting the level of fuel in the engine, allowing a “too lean” or “too rich” air-fuel mixture to persist. This in turn affects the performance of your engine, and can eventually cause the catalytic converter to fail.
Replacing The Oxygen Sensor
It’s worth highlighting that oxygen sensors are extremely durable. Despite the harsh conditions in which they operate (under constant exposure to contaminants), it is not uncommon for them to last over 100,000 miles. That said, when they fail, they must be replaced. Given the importance of this component to the performance of your vehicle – as well as the life of your catalytic converter – an OEM-certified replacement is recommended.
Many auto supply shops sell special sockets that are designed to remove the O2 sensor from its mount. Unless you’re familiar with your vehicle’s exhaust system, however, consider having the component replaced by your mechanic. That way, you’ll be confident the replacement has been installed properly.