How To Know When to Change an O2 Sensor

An automobile's oxygen or O2 sensor is designed to monitor how much unburned oxygen is contained in the exhaust when it exits the engine. This system is used by the car's electronic control unit (or ECU) to determine whether the fuel-to-air mixture being used is correct. While there are several factors that can affect the efficiency of fuel burn, the O2 sensor is usually the first gauge that the engine uses to properly compensate. If you are having performance related problems with your car, like acceleration lag, poor power, and the like, a broken or improperly working O2 sensor might be the culprit.

Auto enthusiasts might be able to diagnose an improperly working O2 sensor from the symptoms. For the uninitiated, here are a few ways.

  1. Your "check engine" light is turned on. This light could be set off for a variety of reasons, most of which correspond to any issue with the engine. Sometimes, it's a leak in your oil gaskets. Sometimes, it's an improperly tuned engine. But whenever your check engine light goes on, this might be a signal that something needs repairing or replacing in your engine, quite possibly the O2 sensor.
  2. You might notice that after a cold start, your exhaust emissions are more hazy than when your car has been running warm for some time. This is because the engine uses a richer mixture of air and gasoline, to compensate for the cooler temperature. But if your car has been running for at least 30 minutes, and you still notice heavy smoke from the tailpipe, this might be a symptom of a broken O2 sensor.
  3. Poor mileage can be another symptom of an O2 sensor that needs replacing. Engines of modern cars are usually smart enough to adjust to the owner's driving style, to maximize fuel efficiency. But if you notice your fuel efficiency drastically drop, it could mean several things. It might mean you need to change lubricants, you need a tune up, or you need to change some sensors like the O2 sensor.
  4. You can try going for an oil change, and you can also change spark plugs and do a tune-up at this point. You can also have your high-tension wires checked. If the exhaust is still dirty, then it's likely an O2 sensor problem.
  5. If you go for your annual car registration, and you do not pass the emissions test, one culprit could be a broken or improperly working O2 sensor. Again, you might want to do an oil change and tune up first, but if it still fails the emissions test, then it might be time to have the O2 sensor checked.

In some cases, emission problems and fuel efficiency issues are related to a failure of the O2 sensor to properly relay fuel mixture information to the car's ECU. This results in inefficient burn, which in turn causes dirty emissions and poor mileage. If you suspect this, then a trip to your friendly neighborhood garage should be your agenda.


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