What Is An Oxygen Sensor And Why Is It Important?
Oxygen sensors are a critical component of the fuel and emissions systems on your vehicle. This tubular device is usually found connected to the exhaust manifold or to the catalytic converters. Subaru vehicles generally have two to five oxygen sensors.
The number of oxygen sensors your Subaru has depends on your model and what engine your vehicle has. Your vehicle's service manual will tell you how many oxygen sensors it has and where they are located.
How Oxygen Sensors Work
The oxygen sensors on your vehicle are crucial to keeping the air-fuel ratio perfect. The oxygen sensor(O2 sensor) is designed to detect the amount of oxygen in the exhaust system. It compares this to the amount of oxygen outside the vehicle. The data is then sent to the vehicle's engine control unit (ECU) which uses the data to modulate the air-fuel mixture.
The ECU does not only use data from the O2 sensors to determine the air-fuel mixture. The ECU also looks at factors such as:
- Engine temperature
- Engine load
- Air temperature
- Throttle position
Symptoms Of A Failing Oxygen Sensor
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When your vehicle's air-fuel ratio is not perfect, it is running too rich or too lean. A rich mixture means there's too much fuel in the mixture. A lean mixture means there's too much air in the mixture. In either case, your engine's performance is compromised as are some of its components. When running too lean, the spark plug's lifespan decreases. Check out our blog post on diagnosing a bad spark plug. It is possible to identify if your engine is running too rich or too lean by checking for symptoms.
Symptoms of a rich mixture are:
- Check engine light
- Poor fuel economy
- Failed emissions testing
- Reduced power and sluggish acceleration
- Strange odors such as the scent of gasoline in the exhaust
- Rough idle
Symptoms of a lean mixture are:
- Check engine light
- Poor fuel economy
- Failed emissions testing
- Reduced power and sluggish acceleration
- Rough Idle
- Long crank and difficulty starting, especially in cold weather
If you are experiencing any of these symptoms, the oxygen sensor is a likely culprit. That is not always the case. There are other components in your vehicle's engine and fuel system that can cause similar symptoms. It is best to do a diagnostic check to narrow down the problem. You can perform one yourself, through a Subaru dealership, or through an independent mechanic. If you conclude that the oxygen sensor is the cause, you can find a replacement here.