Understanding your car's lifespan: O2 sensors – what are they and how long do they last?

<i>Image: iStock</i>
<i>Image: iStock</i>

Stricter environmental controls and the requirement to create less pollution has led to far more complex automotive exhaust systems. One component of these systems is the oxygen sensor or Lambda sensor.

Dewald Ranft, Chairman of the Motor Industry Workshop Association (MIWA), an affiliate association of the Retail Motor Industry Organisation (RMI), explains that depending on the make and model you drive, you could have one or more oxygen sensors in the exhaust system.

Too rich or too lean

Ranft said: "This sensor measures the amount of oxygen in the exhaust gas and sends this information to the car’s computer. The computer then works out if the engine is running too rich (too much gas) or too lean (too much air) and adjusts to compensate."

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Because the sensors are exposed to very high temperatures when the engine is running, even if the vehicle is parked and idling, they will begin to deteriorate over time.

"In addition to high heat, the sensors can also be affected by contaminants in the exhaust, excessive amounts of unburned fuel in the system and other things. It’s important that vehicle owners know that there are sensors in their car and that they don’t last forever," says Ranft.

Look out for the signs

He adds that generally oxygen sensors last between 80 000 and 100 000 kilometres: "However, if your engine is properly maintained, the sensors can last longer.

"Most late model vehicles do not have a recommended replacement interval for oxygen sensors. Some oxygen sensor manufacturers do say that replacing the sensors at high mileage is a good way to assure peak performance and fuel economy."

While the average vehicle owner won’t know when the sensors are faulty, especially if there isn’t a Check Engine light or any codes that might suggest an oxygen sensor related fault, Ranft says there are some commons signs to watch out for including: the engine idles rough or sputters when releasing the accelerator; reduced fuel economy; loss of power from the engine and sluggish engine performance.

Check out this 40 second video about the symptoms of a bad oxygen sensor:

“If you’re experiencing any of these things, it’s important to have your car inspected and the sensors replaced if necessary. A faulty oxygen sensor can lead to premature damage to expensive parts of the engine system. When replacing an oxygen sensor, it’s important to use the same type as the original.”

He recommends taking your vehicle to an accredited-MIWA workshop where the mechanic can read the oxygen sensor's output with a scan tool or digital voltmeter. “Oxygen sensors are amazingly rugged considering the operating environment they live in.

                                                                            Image: iStock

But they do wear out and eventually have to be replaced. Ask your mechanic to check the sensors during your regular maintenance services. The only way to know if the oxygen sensors are doing their job is to inspect them regularly.

There may also be benefits to replacing the sensors periodically for preventive maintenance. Replacing an aging oxygen sensor that has become sluggish can restore peak fuel efficiency, minimise exhaust emissions and prolong the life of the converter,” he concludes.

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