If an oxygen sensor fails, the engine computer won’t be able to correctly set the air-fuel ratio, which could result in lower fuel economy, higher emissions and damage to other components, such as an overheated catalytic converter.

The Oxygen O2 sensor is located in your vehicle’s exhaust system, usually on the exhaust manifold or close to the engine. There may be several oxygen sensors on your vehicle. These sensors are always located in the exhaust gas flow of your vehicle.

Here are some of the most common signs that your oxygen sensor is bad.

• A Glowing Check Engine Light. The bright orange Check Engine light in your dashboard will usually glow if you have a bad oxygen sensor.
• Bad Gas Mileage.
• An Engine That Sounds Rough.
• An Emissions Test Failure.
• An Older Vehicle.

A decrease in fuel efficiency can be a telltale sign that an O2 sensor is not performing as it should. This can happen because of a fuel mixture that is either too lean or too rich. Such a swing in A/F ratio is a sign that an upstream or control sensor is faulty.

If you decide to do the repairs, the cost to replace the oxygen sensor yourself can be between $20-$94, depending on the brand and type of sensor you buy. To have the repairs done by a mechanic the price can be anywhere between $113 to $478 for parts and labor.

Can You Drive With A Bad Oxygen Sensor? Yes, you can drive with a bad oxygen sensor if you can still start your engine and feel little difficulty driving. But don’t leave it alone for over a couple of days, as it might cause safety problems and lead to the malfunction of other parts of your vehicle.

If you have noticed some bad O2 sensor symptoms and are ready to replace your sensors, AutoZone has everything you need to do the job right. Of course, if you have questions about your O2 sensors or anything else automotive, our knowledgeable AutoZone associates are always ready to help.

In most vehicles, replacing an oxygen sensor is a simple procedure that requires only a few tools. However, if this is not a task you are comfortable doing on your own, this is something that any professional technician, such as one from YourMechanic, can take care of quickly and easily.

O2 sensor failures can be caused by various contaminants that enter the exhaust. These include silicates from internal engine coolant leaks (due to a leaky head gasket or a crack in a cylinder wall or combustion chamber) and phosphorus from excessive oil consumption (due to worn rings or valve guides).

It shouldn’t take more than 1/2 hour for the whole job to be done.

Do You Need A Special Tool To Remove O2 Sensor? No, you don’t need a special tool like the stripped o2 sensor removal tool to remove your vehicle’s O2 sensor. Although nothing beats using the right tools for the right job, you could easily remove it without a special tool.

If you disconnect the front sensor, you’ll run as rich as the fuel tables will allow. Be design it won’t hurt anything, but you could run so rich that you wash down the cylinder walls and score the heck out of them which means its rebuild time. If you disconnect the rear sensor you’ll just throw a couple of codes.

Things You’ll Need

1. New oxygen sensors.
2. Jack.
3. Jack stands.
4. 3⁄8 in (0.95 cm) ratchet wrench or open end wrench.
5. 7⁄8 in (2.2 cm) oxygen sensor socket.
6. Penetrating oil.
7. Auto diagnostic scanner/reader (optional)
8. Flathead screwdriver (optional)

It is best to replace your sensors in pairs. For example, if you replace the downstream left sensor, you should also replace the downstream right. However, on most vehicles produced since 1996, replacing one sensor (especially the front engine monitoring sensor) will cause the ECU to set a code for the other sensors.

“Bank 1, Sensor 2” is the rear oxygen sensor. A V6 or V8 engine has two banks (or two parts of that “V”). Usually, the bank that contains the cylinder number 1 is called “Bank 1.”

The O2 sensor in your vehicle monitors the exhaust gases coming out of the engine. Once you’ve replaced your vehicle’s O2 sensor, you’ll need to reset the ECU so it can properly gather information from the new O2 sensor.

Oxygen Sensor Test

1. Identify the specific o2 sensor that you want to do the oxygen sensor test on.
2. You will need a 10-megaohm impedance digital voltmeter for testing the o2 sensor.
3. Now start the car and let it run until it reaches operating temperature.
4. Once you have reached operating temperature, turn off the engine.

Will a new o2 sensor improve performance? As O2 sensors age, they slow down. So when an O2 sensor fails prematurely, the cause is often contamination. But replacing the O2 sensors will only temporarily restore the fuel feedback control system.

To the original question: The only way the ECU knows a cat is bad by the readings it get from the O2 sensors. A bad O2 sensor will indicate that the catalytic converter is bad. If the code indicates a bad cat…then further tests need to be run to determine if it’s a bad O2 sensor or a bad cat.