One of the key components to keeping good fuel economy and low emissions is the oxygen sensor. It provides feedback to your engine computer to keep your air-fuel ratio balanced, and it can also cause major issues when it needs to be replaced.
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You may not think about these sensors until it’s too late, so we’ve gathered the most common issues with oxygen sensors.
Knowing what to look for will help keep your car on the road.
#1 – Your Check Engine Light (CEL) Illuminates In The Gauges
The Check Engine Light (CEL) is a key sign that you have an issue that needs to be addressed.
Until you use a diagnostic scanner to identify the trouble code being stored in the engine computer, you won’t know the oxygen sensor is the problem.
How to Fix It
The Check Engine Light illuminates when the engine computer determines that something is out of range. If the oxygen sensor readings are out of their operation window because of poor emissions or a faulty sensor, the CEL will illuminate to signal a problem.
You can use a hand-held diagnostic scanner to check the trouble codes being stored in the computer.
There are several trouble codes associated with oxygen sensors.
- Codes P0030, P0031, P0130, P0131, P0132, P0133, and P0134 are linked to oxygen sensors
- Codes P0140, P0141, P0161, or P0172 can be related to an air-fuel mixture discrepancy
Once you have determined the sensor is faulty and needs to be replaced, you disconnect the wire harness connector and use either a wrench or a deep socket with a cutout for the wiring harness to unthread the sensor from the exhaust pipe.
Be sure to add a small amount of anti-seize to the threads of the new sensor when you install it.
#2 – You Recognize A Decline In Fuel Economy
Your fuel economy is a direct result of optimizing the performance of your engine and its ability to effectively burn the air-fuel mixture in the combustion chamber. Burning more fuel for the same output will cause a decline in your fuel economy or miles per gallon.
How to Fix It
A defective oxygen sensor may not trigger a check engine light, but it can still cause your fuel mileage to go down. Oxygen sensors should be replaced between every 60,000 – 90,000 miles, and in that range, you could see a decline in your fuel economy without a check engine light illuminating.
Replacing oxygen sensors is an easy task using a wrench or a deep socket designed to accommodate the wiring harness.
The sensors thread into the exhaust pipe. You may have two, three, or four sensors in your exhaust system, and they should be replaced as a complete set.
#3 – Your Engine Has A Rough Idle Or Stalls Frequently
Your car engine should idle between 750 – 1,100 RPM when it is at operating temperature. If your car engine idles above or below that range or constantly surges up and down, your oxygen sensors may be giving faulty readings to the computer.
How to Fix It
Many different sensors send signals back to the engine computer to regulate idle and fuel mixture.
A bad sensor can send incorrect information to the computer that can cause it to hunt for the correct idle, can cause it to adjust the fuel-air mixture, and it can even cause the engine to stall.
Most hand-held scanners only read trouble codes stored in the engine computer, so a bad sensor may not be detected. Service centers may have diagnostic equipment that can read the sensor output to understand if the information is faulty and the sensor is bad.
Changing the oxygen sensors just needs basic hand tools, and the complete set of sensors should be changed at the same time.
#4 – Your Engine Performs Poorly
One of the things you count on from your car is its performance. When you step on the gas pedal, you expect it to get up and go.
Faulty oxygen sensors can restrict that performance and you may lose the acceleration when you need it most.
How to Fix It
If you drive around town from stoplight to stoplight, you may never put the pedal to the metal and unleash your car engine’s full performance. At part throttle, the engine will run just fine.
It’s only when you give it everything it has, does it fail to perform.
A lack of performance will get worse over time if left alone. If you notice the problem, it may be accompanied by a misfire, sputtering, popping, and eventually it may stall the engine completely.
The best course is to have your car check for stored diagnostic trouble codes if the Check Engine Light (CEL) hasn’t illuminated already. If any of the codes associated with the oxygen sensors have been stored in the computer, the sensors should be replaced with new ones.
#5 – You Fail An Emissions Test
Some counties or states require an emissions test every 1 to 2 years to verify you still have working emissions equipment on your car. Oxygen sensors are part of that equipment, and if they are faulty you may fail the testing and require repairs before retesting again.
How to Fix It
Emissions testing uses a probe inserted into the tailpipe of your car to check the number of pollutants in the exhaust.
This testing, also called a smog check, measures the amount of hydrocarbons, oxygen, carbon monoxide, and nitrogen oxides in the exhaust gas after the combustion process.
A faulty oxygen sensor can give false readings and upset the balance of the air-fuel mixture in the combustion chamber. This can lead to higher pollutants left in the exhaust gas that can only be registered by the emissions testing.
A failed report isn’t the end of the world. It may just mean you need to replace the oxygen sensors in your emissions system, and it will restore the air-fuel balance in the combustion process.
#6 – Your Catalytic Converters Fail Prematurely
Another part of the emissions system is the catalytic converters. The exhaust gases heat the honeycomb inside the converter housing that provides an additional burning process for the exhaust gases.
These can fail prematurely due to faulty oxygen sensors, and they are not cheap to replace.
How to Fix It
Faulty oxygen sensors can cause the air-fuel mixture to be rich, meaning it has too much fuel in the combustion process. That excess fuel doesn’t fully burn in the combustion process, and it can then travel to the catalytic converters to cause damage.
You may think it isn’t worth the trouble to fix an air-fuel imbalance, but replacing a catalytic converter isn’t cheap. They can cost hundreds or thousands of dollars to replace, while oxygen sensors can be as low as 30 dollars each.
If you detect black smoke from the exhaust pipe or a rotten egg smell from the exhaust, you should have your car checked for bad catalytic converters or bad oxygen sensors. You’ll want to have the faulty components replaced as soon as possible.
#7 – Your Engine Overheats
Most attribute an overheating engine to a failing cooling system, and they are usually correct in that line of thinking.
One thing that can contribute to the problem of overheating is faulty oxygen sensors, and they can in some cases be what started the problem in the first place.
How to Fix It
Your car running a little hot in the summer may be normal because you’re stuck in stop-and-go traffic. Be sure to check the coolant level in the cooling system when the car is cold to ensure overheating isn’t caused by a lack of coolant.
Also, look for other tell-tale signs that the oxygen sensors are causing the problem. Your car is most likely running a lean air-fuel mixture in the combustion process and it’s overheating the engine.
The spark plugs may be white in color indicating they are running hotter than intended. Replacing the oxygen sensors will return the combustion process air-fuel mixture to normal and should stop overheating the engine.
#8 – You Hear Strange Sounds From The Engine
Some engines are excessively noisy, and it may be difficult to determine if the engine is making strange sounds while it is running.
A clicking or tapping noise can be caused by the cylinder heads if they are cold and not fully oiled. One thing you should never hear is popping from the exhaust tailpipe.
How to Fix It
Faulty oxygen sensors can cause a rich or lean condition in the combustion process.
- A rich condition can cause a buildup of carbon residue on the spark plugs and valves in the cylinder head.
- A lean condition can damage spark plugs and also cause a misfire or detonation to occur.
Any of these cases can lead to overheating and damage to the engine.
A dirty air filter and dirty fuel injectors and/or fuel filter can also cause an air-fuel mixture problem, so take your time diagnosing the problem, and replace all components required to fix the problem before it gets worse.

