Lambda sesnor measures the amount of oxygen in the exhaust gas and sends this information to the car’s computer. File photo: Ralf Gromminger
Johannesburg - 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, explained that depending on the make and model you drive, you could have one or more oxygen sensors in the exhaust system.

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

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," Ranft said. "It’s important that vehicle owners know that there are sensors in their car and that they don’t last forever."

And this is what they actually look like. File photo: Bosch

Oxygen sensors last between 80 000 and 100 000 kilometres, he said.

“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, although sensor manufacturers do say that replacing them 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 said there are some common signs to watch out for including: the engine idles rough or sputters when releasing the accelerator; increased fuel comnsumption, loss of power from the engine and sluggish engine performance.

“If you’re experiencing any of these things, it’s important to have your car inspected and the sensors replaced if necessary," he advised. "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.”

Amazingly rugged 

He recommended taking your vehicle to an accredited workshop where the mechanic can read the oxygen sensor’s output with a scan tool.

“Oxygen sensors are amazingly rugged considering the operating environment they live in," he said. "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.”