We don’t typically cover a lot of topics related to auto tools and issues, but the oxygen sensor keeps coming up on my project list. Knowing how to replace an oxygen sensor in your vehicle can save you both money and hassle.
Why Replace an Oxygen Sensor?
With all the computer accessories in today’s cars, many car problems can seem overwhelming. It’s frustrating when your car’s check engine light comes on, especially for something as seemingly simple as a broken oxygen sensor. This is particularly true if your car has over 100,000 miles on it. The normal life expectancy of an oxygen sensor is approximately 60 to 90,000 miles.
But here’s the good news: there’s not much chance of messing up your vehicle with an oxygen sensor replacement. So by trying to do the job yourself, you can definitely save a few bucks.
What is an Oxygen Sensor?
Every new car, and most cars produced after 1980, is equipped with at least one oxygen sensor. These sensors provide data to the car’s engine-control computer and are crucial for the emissions system. The purpose of these sensors is to keep the engine running as efficiently as possible and minimize pollution.
Gasoline engines burn fuel and oxygen. The mixture of fuel and air is known as the fuel-to-air ratio, and it’s critical for proper engine performance. This ratio varies depending on factors like fuel quality, fuel composition, altitude, and temperature.
If the air-fuel mixture is unbalanced, there may be excess fuel after combustion, resulting in a “rich” blend. This is undesirable because unburned fuel can lead to excessive fouling of the tailpipe and waste fuel. On the other hand, if there’s too much air in the mixture, it is considered a “lean” mixture. Leaner mixtures generate more nitrogen oxide pollution, which can cause poor engine performance and even engine damage. Oxygen sensors play a vital role in determining the precise air-fuel ratio your car needs at any given time.
Replacing the Oxygen Sensor
The oxygen sensor is typically located in the exhaust pipe, with most modern cars having one before and after each catalytic converter. Catalytic converters are an essential part of the emissions and pollution control system.
The oxygen sensor is positioned directly in the exhaust stream and measures the concentration while the engine is running. It then sends this data back to the car’s engine-control computer, which makes any necessary adjustments.
As you drive, the engine computer constantly optimizes the engine’s performance and fuel efficiency. External factors such as altitude, air/engine temperature, barometric pressure, and engine pressure can also affect how the engine operates.
It’s frustrating when the engine light comes on. Many times, when you visit a service technician, they’ll tell you it’s an oxygen sensor problem. Keep this diagnosis in mind when you receive it. When the oxygen sensor is not functioning properly, the engine control computer defaults to a mode that ignores all variables because it doesn’t receive the necessary data. This can result in poor fuel economy, diminished performance, and increased vehicle pollution.
Diagnosing Problems Using an OBD2 Scanner
If you have even basic mechanical skills, you might be able to replace the oxygen sensor yourself. It starts with diagnosing why the check engine light came on in the first place. If you have your own engine code reader, this is very easy. We highly recommend the Innova CarScan Pro OBD2 scanner.
Many national discount auto parts retailers offer free basic diagnostic services to tell you why your engine light is on, as they hope to sell you some parts. Additionally, your regular mechanics and service technicians can perform diagnostics on your car. If you prefer not to get your hands greasy and plan to take your car to a mechanic first, that’s also possible. Regardless, once you know the problem, you can choose the appropriate oxygen sensor.
We highly advise against selecting cheap products, as they don’t last. Sadly, I had to learn this the hard way! Nowadays, I only buy Bosch or OEM (Original Equipment Manufacturer) oxygen sensors.
Replacing the Oxygen Sensor
Now that we’ve covered the theory, let’s get down to business. We’ll show you how to replace an oxygen sensor using our test car, a latest model Honda Civic. According to my OBD2 code scanner, we received a diagnostic code related to the secondary oxygen sensor.
After stopping at a local parts store, we picked up a Bosch replacement with a factory-style plug. Since oxygen sensors have wires on the end, you can’t use a traditional box or box wrench. For this job, we invested in a practical kit from the parts store that includes three different oxygen sensor sockets for just over $20. These sockets should work with almost all oxygen sensors since most have a 7/8″ (22mm) hex driver.
The reason for having three different sockets is that car manufacturers don’t always consider accessibility when assembling the car at the factory. As a result, changing them sometimes requires using crazy angles and adapters.
For the Honda Civic, the secondary oxygen sensor is located in a fairly open and accessible area at the front of the engine. So, we used a socket-style socket tool that fits over the sensor and allows room for the power cord to pass through. Before removing the sensor, we unplugged it from the wiring harness.
Sometimes, unplugging the sensor can be challenging. Be patient and careful when separating the plug halves to avoid damaging either the plug or the wire. Using a 3/8″ drive ratchet, we were able to easily loosen the old sensor.
To install the new sensor, simply screw it on and plug it back into the wiring harness using the appropriate socket adapter. Once everything was set, we used AutoScanner to clear the codes stored on the engine computer, and then started the car. After driving around the neighborhood for a few laps, the check engine light stayed off, indicating a successful replacement and a healthy car.
By following these steps, you can save both money and hassle by replacing the oxygen sensor in your vehicle yourself.