We don't usually cover too many auto tools and issues. However, the oxygen sensor keeps coming back to my project list. Knowing how to replace an oxygen sensor in your vehicle can save you a lot of money and hassle.
With all the computer accessories in cars these days, many car problems can seem daunting. Don't you hate it when your car's check engine light comes on? Usually it's for something relatively simple like an oxygen sensor, but it's broken. This is especially true if your car has approximately 100,000 miles or more on it. The normal life expectancy of an oxygen sensor is approximately 60 to 90,000 miles.
good news? There won't be much chance of messing up your vehicle with an oxygen sensor replacement. So you can definitely save a few bucks by trying to do the job yourself.
What is an Oxygen Sensor?
Every new car, and most cars produced after 1980, has at least one oxygen sensor, if not more. These sensors feed data to the car's engine-control computer and are an important part of the emissions system. The idea behind these sensors is to keep the engine running as efficiently as possible and producing as little pollution as possible.
All gasoline engines burn fuel and oxygen. This mixture of fuel and air is critical and is known as the fuel-to-air ratio. This ratio will vary with many different variables such as fuel quality, fuel composition, altitude and temperature to name a few.
If the air is not balanced, there may be residual fuel after combustion. We call this a "rich" blend. You don't want this, as unburned fuel can lead to excessive fouling of the tailpipe. Frankly, it's a waste of fuel.
If there is too much air in the mixture, it is said to be a "lean" mixture. Leaner mixtures create more nitrogen oxide pollution. In some extreme cases, this can lead to poor engine performance and even engine damage. All in all, oxygen sensors play a key role in determining the exact air-fuel ratio your car needs at any given time.
replace oxygen sensor
The oxygen sensor is located in the exhaust pipe. Most modern cars have one before and after each catalytic converter. Catalytic converters are another topic of discussion. Just know that they are a necessary part of your emissions and pollution control system.
The oxygen sensor is located directly in the exhaust stream and detects the concentration while the engine is running. They then transmit this data back to the car's engine-control computer. It then makes any necessary adjustments.
As you drive, the engine computer constantly makes changes to optimize the engine's performance and economy. Many external factors can also affect how an engine operates. This includes altitude, air/engine temperature, barometric pressure, and even engine pressure.
We all hate it when the engine light comes on. Many times, when you go to a service technician, he will tell you that it is an oxygen sensor problem. Be aware of this diagnosis when you get it. When the oxygen sensor is not working properly, the engine control computer defaults to a mode that ignores all variables. It can't because it doesn't get the data it needs. This can lead to poor fuel economy, poor performance, and extra pollution from your car or truck.
Diagnosing Problems Using an OBD2 Scanner
Now all of this is to say that if you have the slightest twist of a wrench, 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. This is very easy if you have your own engine code reader. We love Innova CarScan Pro OBD2 scanner.
Many national discount auto parts retailers also offer basic diagnostic services for free. They do it because they're happy to tell you why your engine light is on so they can sell you some parts. And of course, there are your regular mechanics and service technicians who can perform diagnostics on your car. Now, if you're taking your car to a mechanic first, we're guessing you'd rather not get your hands greasy. No matter how you know it, once you know it, you can buy it.
We advise against choosing cheap products. They don't last. Unfortunately, I had to learn this the hard way! I now only buy Bosch or OEM (Original Equipment Manufacturer) oxygen sensors.
replace oxygen sensor
Now that we've covered the science lesson of this article, we can get down to what we're going to do. Let's replace an oxygen sensor. Our test car is a latest model Honda Civic. According to my OBD2 code scanner, we got 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 the oxygen sensor has some wires on the end, you can't use a traditional box or box wrench. Wires blocked the way. For this job we picked up a nifty little kit from the parts store that has three different oxygen sensor sockets for just over $20. Since most oxygen sensors have a 7/8" (22mm) hex driver, this kit should work with almost all oxygen sensors.
The reason for using three different sockets is that when they assemble the car at the factory, they don't always consider accessibility in the event that maintenance needs to be done in the future. Sorry to say, when it comes time to change them, it sometimes takes some crazy angles and adapters to get things right.
For the Honda Civic, the secondary oxygen sensor is located in a fairly open and accessible area at the front of the engine. Since this is the case, we used a socket-style socket tool that fits over the sensor and leaves room for the power cord to pass through. We unplug the sensor from the wiring harness before unhooking it.
Use oxygen sensor socket
Sometimes unplugging the sensor can actually be the hardest part of the job. Be patient and careful when pulling the plug halves apart so you don't damage the plug or the wire. Using the 3/8" drive ratchet we were able to easily loosen the old sensor.
Installation is the exact opposite of removal, simply screw on the new sensor and plug it back into the wiring harness using the appropriate socket adapter. Once we were all set, we used AutoScanner to clear the codes stored on the engine computer, and we started the car. After a few laps around the neighborhood, the check engine light didn't come back on and the car was healthy again.