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Oxygen Sensor?

Hi guys. Please humor me as I don’t know anything about cars.

My car’s check engine light comes on if I drive it between farther than five miles. It shuts goes off again if I shut off the car but if it was recently run it comes back on quickly.

My mechanic says this it’s the oxygen sensor. Is this important? Is this expensive? I’m loathe to drive it any long distance (especially on the highway) for fear that my car will explode.

I’d appreciate any advice.

You don’t say what type of vehicle, but here’s the basics.

Your vehicle has two or more O2 sensor. These sensors are positioned before and after the catalytic converter(s). The sensor(s) positioned before the catalytic converter(s) adjust the fuel mixture to the engine. The sensors after the cataytic converter(s) monitor the catatytic converter(s) efficiency. So if the problem is with a sensor positioned before the cat, it can have an effect on fuel mileage. The sensor(s) after the cat have no effect on fuel mileage.

So, your car won’t explode. But you could be wasting fuel. And if the problem is with a sensor before the cat, it can result in damage to the cat. But get it fixed. Because a vehicle with a Check Engine light on is not a properly operating vehicle.


Don’t worry. A bad oxygen sensor will just make you burn more fuel if it is one of the front ones, or just prevent you from passing emissions if it is a rear one. The front ones are used to adjust the fuel mixture, and if bad, will cause the computer to use a richer mix. The rear ones only monitor the catalytic converter efficiency.

The oxygen sensor is not causing the engine shut down. Something else is.

Tell us about your car: make, model, year, and if it’s a 4 or 6 cylinder engine. If you know the engine size, tell that, also.

Get the codes for the check engine light and tell us what they are. Some auto parts stores will read the codes, for free.

Check engine light comes on. Mech says O2 sensor. Is it important? If you don’t change the O2 sensor, you will be changing the cat and the O2 sensor. How important? Gasoline cheap your location. Yes? Keep driving.

Thanks for your help guys. I understand a little better.

It’s a 93 Honda Civic. I believe it’s a V4. I’ve recently had the Catalytic Converter and EGR replaced to pass emissions.

I haven’t been able to get the code read by a computer. Midas said they’d have to take off a fender and that would cost a lot.

Your vehicle has the OBDI engine management system. This means there’s only one O2 sensor. Replace the sensor and disconnect the negative battery cable for 30 seconds to erase the code and it should be good to go.


“It’s a 93 Honda Civic. I believe it’s a V4”

Whatever you do, don’t ever sell that car as it is very rare, since Honda has never manufactured a car with a V-4 engine!

Seriously, however, your engine is an I-4, meaning that the cylinders are aligned in a straight line, rather than in a V-formation.

There is nothing wrong with knowing nothing about cars, but it is important that you not reveal this lack of knowledge to a mechanic or a service writer, as an unscrupulous one (like those at Midas, Meineke, Monro, Sears, Aamco, Lee Myles, Cottman, Tires Plus, and essentially all of the other chain operations that work on a commission basis for the mechanic and the service writer) will use this as a signal to take you like Grant took Richmond. If you go to a well-reputed independent mechanic, you are much more likely to have good-quality repair work done at a fair price, as opposed to going to Midas.

In other words, don’t offer information that will reveal your lack of automotive knowledge, such as, “I believe that my engine is a V-4”, or “I think that the problem may be in my XXXXXXXX”. If you offer a solution that is really off-the-wall, this is also a signal that you are ripe for the picking. Just describe the symptoms, ask what they believe the remedy to be, tell them that you will think it over, and then come back to this site in order to verify the accuracy of what you were told. Just offer the required information, listen carefully (possibly take notes), and then allow people on this site to help you.