The oxygen sensor was one of the first components integrated onto vehicles to monitor exhaust emissions. Since the implementation of OBD II (on-board diagnostics two) in 1996, oxygen sensors on vehicles have doubled and quadrupled. One sensor is placed near the exhaust manifold, and many cars have two manifolds--one on each side of the motor. Another sensor now regulates the efficiency of the catalyst, downstream in the exhaust system. Since sensors exist in hostile environments, they only last so long.

What the Sensors Do

Oxygen sensors were integrated into exhaust systems in the '70s. A single wired component at the time, the sensor sent a voltage signal to the computer of the vehicle to communicate the fuel-to-air ratio. The older sensors didn't send the signal to the computer until the engine reached operating temperature. Nowadays, three- and four-wired sensors have internal heaters to heat up more quickly. They begin transmitting data almost immediately. Because of the environment they work under, the tips of the sensor inside the exhaust system can build up carbon and other pollutants and burn. Wires can also be compromised under the intense heat emitting from the exhaust system, which compromises the voltage output of the sensor. When the sensor fails or is compromised, the computer cannot make the necessary adjustments to the fuel-to-air ratio and more pollutants are expelled from the exhaust system. In addition, because the mixture will run too rich or too lean, other components, like the catalytic converter, can become damaged.

The Durability of the Sensor

The oxygen sensors are much more durable nowadays than when they were first used. The single-wired sensors had a shelf life of 30,000 to 50,000 miles. The three- and four-wired sensors of today can last up to 100,000. Keep in mind that sensor failure can occur in two ways. Sensors can simply fail from age and normal wear and tear. However, a poor performing engine can also cause damage to a sensor. In this case, replacing the sensor does not fix the overall problem with the engine. Diagnosing the correct trouble code to identify the problem is crucial to the new sensor's existence. If a sensor is installed into the exhaust system with an underlying problem in the engine, it will only be a matter of time before that sensor also fails.

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Oxygen Sensors

Oxygen Sensors and Emissions

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