How To Fix Your Car’s Oxygen Sensor

Oxygen sensors are a vital component for the proper functioning of vehicles, as they enable the engine to get the fuel-air mixture. Over time, oxygen sensors may become unresponsive or faulty and cause the “check engine” light to activate; unfortunately, these sensors cannot be repaired as they contain delicate technology and materials. Replacing a faulty oxygen sensor is the only viable solution to get your car running properly again. To this end, this article provides a step-by-step guide on how to replace a faulty oxygen sensor.

How Do Oxygen Sensors Work?

Oxygen sensors are a key part of the vehicle emissions system. They measure the differential oxygen levels between the outside air and the exhaust gas to generate a voltage which is relayed to the vehicle's central computer. This data is used to determine the fuel-to-air ratio of the engine and make the necessary adjustments based on the driving conditions. Depending on the vehicle or engine type, there may be up to four oxygen sensors.

Why Replace A Faulty Oxygen Sensor?

A faulty sensor cannot transmit accurate data to the car's computer, causing the engine to run unbalanced. An unbalanced engine either burns fuel with too much or too little air. When there is too much air in the fuel, the engine runs lean, leading to issues such as delays in acceleration, jerking, rough idling and stalling. 

Similarly, when there is too little air in the fuel, the engine is running rich and burning more fuel, becoming hot and generating more pollution. An imbalanced engine also puts an extra strain on other components, including the catalytic converter, and can lead to costly repairs.

How To Replace A Faulty Oxygen Sensor

Tools Required

First, you will need an onboard diagnostic (OBD II) scanner to identify the problem. That’s because other issues, such as a failing catalytic converter, a loose gas cap, or a disconnected vacuum hose can trigger the "check engine" light. Hence you will have to diagnose the system to identify the actual problem.

You will then need the following tools to successfully replace the faulty sensor:

• Wrench
• Jack and jack stand to lift and support the vehicle
• A new oxygen sensor to replace the faulty one
• An Oxygen sensor socket
• Hand gloves

Replacing The Faulty Sensor

• Since the vehicle may have between 2 to 4 sensors, use the OBD II scan tool to diagnose which oxygen sensor is faulty. Depending on the car, the sensors will be located on both sides of the engine, or before or after the exhaust system.
• Once you have identified the faulty sensor, park the vehicle on a leveled surface and lift it with the jack, then support it with a jack stand to keep it elevated. Be sure to raise it on the side where the faulty sensor is located.
• You will find a plug towards the end of the sensor cable that is connected to an outlet. Pull it out to disconnect the oxygen sensor from the car's electrical system.
• Use a wrench to loosen the oxygen sensor and remove it. Due to the heat from the engine and exhaust system, the sensor might seize up and become difficult to remove. Spray a lubricant where the sensor will be unscrewed to ensure easy removal.
• Most new oxygen sensors come with an anti-seize gel to help make it easier to unscrew when the time comes to remove it. Apply a small amount of the gel to the thread of the sensor before fixing it.
• Fix the new sensor in place of the old one and screw it firmly into place. Do not over-tighten to avoid stripping the thread.
• Now plug the wiring harness of the new sensor into the car’s electrical system. It should be plugged into the same port where you unplugged the old sensor.
• Once the sensor is fixed, start the car to confirm if the problem is gone. If so, the “check engine” light should go off. Also, you should no longer experience the symptoms of a faulty oxygen sensor. Note that for some vehicles, you will have to turn off the light manually by clearing the error codes. Connect the OBD II scan tool to clear the codes.

This is how you go about a faulty oxygen sensor. It’s a straightforward procedure. However, have a professional mechanic attend to it if the problem persists or if you’re not comfortable replacing it yourself.

Summary

It is vital not to ignore a faulty oxygen sensor. Without a properly functioning sensor, your vehicle's engine will be running on an unbalanced fuel-air mixture which can lead to low engine performance and fuel economy, stalling, and damage to the engine and catalytic converter. Happily, fixing a faulty oxygen sensor is not a difficult task. Once you’ve been able to identify the problem, all that’s left is to unscrew and unplug the old sensor and replace it with a new one.

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