How to Replace Oxygen Sensors

An oxygen sensor, abbreviated as O₂ sensor, is a device that is installed for determining the air fuel ratio in an automobile. In an engine, this electronic device is positioned near the exhaust pipe. It indicates the air-to-fuel ratio of the exhaust gases, rather than the concentration of oxygen entering the engine.

For every combustible engine, the vehicle's mileage depends upon the air and fuel composition. An oxygen sensor helps to examine the engine performance of a car by indirectly measuring the amount of oxygen.

For an O₂ sensor to get activated, high temperature of about 350 degrees Celsius is required. In case of a rich mixture with high amount of partially oxidized components, the device reads a high voltage, while it indicates low voltage for a correct air-fuel composition (lean mixture). Overall, for every engine, a well-functioning oxygen sensor is necessary.

Regular testing of the sensor is advisable in order to prevent excess fuel consumption (poor mileage). On an average, the estimated lifetime of a heated sensor is about 100,000 miles, while that of an unheated model ranges from 30,000 to 50,000 miles.

Similar to any other technology, an O₂ sensor needs to be replaced over a period of time. Eventually, the contaminants like dust and dirt accumulate in the tip of the sensor, which decreases the sensitivity of the device. Also, environmental factors like water and mud may damage the sensor.

Some of the signs of a bad sensor are: dark-colored exhaust gases, increased exhaust emission, obnoxious smell coming from the exhaust gases, reduced fuel economy, and poor engine performance.

Under such cases, you can consider replacing these devices for restoring the peak fuel efficiency, leading to reduced emissions and increased durability of the converter. Since these sensor helps in analyzing the composition of the exhaust gas, they is also an important tool for controlling pollution.

For their replacement, you need to open the exhaust manifold, and disconnect the electrical connector and ground battery cable. Then, remove the old sensor by using the sensor socket. O₂ sockets are available in any mechanical store. Adjust it properly over the sensor, and turn it anticlockwise.

If it is very hard to loosen, then you can slightly warm up the engine, or heat the base of the sensor for an easy removal. Removing the old sensor could also be done using a ring spanner of the right size. A tap with a rubber hammer might loosen it up. Once you remove the old one, you can fix the new O₂ sensor by plugging the wires to the connector.

Apply some amount of anti-seize compound on the threads of the new sensor. This helps in easy removal of the sensor during the next replacement. Fix the sensor and tighten as per the requirement. Following this, you can connect the electrical connector that is similar to the original wiring connections.

You can wipe the sensor and its base for cleaning contaminants (if any). This way, you can replace the O₂ sensors. The information as to when such sensors should be replaced depends on the model of the vehicle and the type of the sensor.