Oxygen sensors

Does anyone have experience with choosing and installing oxygen sensors for a 95 tercel? What is necessary; heated or unheated, exact fit or universal fit,etc. The heated, exact fit, etc. is the most expensive. I believe there are two sensors for this car. My check engine light is on, and someone at advanced auto parts checked it and said it was the pre-catalitic converter sensor, then tried to sell me the sensor for $99. It looks easy to get to the part, so I want to buy it and install it. Any advice is appreciated.

Simply buy the sensor that’s listed in the catalog for your specific application. The parts store guy will look it up for you. It should be 'direct fit".

They’re really easy to replace, but they do take a bit of muscle power usually. I would look up a tutorial online. As for finding the part, I would look it up online myself at Advanced Auto Parts or Autozone for your make and model. Then you can see the listing of parts for yourself. $99 is about in the ballpark, oxygen sensors are not cheap. A low end O2 sensor is probably closer to $68. I wouldn’t skimp on this part. It’s very much responsible for gas mileage and spending the extra money will more than pay for itself.


Some O2 sensors require a special tool in order to replace them. Here’s an example http://www.sjdiscounttools.com/vehicle-specialty-tools-exhaust-system-service-tools-oxygen-sensor-tools.html


As already stated, this sensor has a lot of influence on fuel consumption. A cheap part may cost more over time. I suggest an exact fit.

As for heated or unheated, the parts store should have that answer. The new sensor should be like the original, and have the same number of wires. It may look different, but it’s fine as long as it plugs in like the original.

I replaced one recently; it was quite easy. If you can’t get a wrench around it, you’ll need a special tool; the parts store should have a selection.

I’ve got several O2 sockets, etc. and never use any of them. It was far easier for me to cut the wire off (and break the porcelain off if need be) followed by using a box end wrench on it.

A nearby aircraft salvage sells used tools by the boatload and on the cheap. I give 5 bucks for a top quality and well-used wrench and bend it to whatever is needed.

You should also keep in mind your car’s problem may not even be the O2 sensor at all. The parts counter guys are not mechanics and the fact your car is spitting out an O2 code does not mean the O2 is bad.

So what code, or codes, were you given?

Corrosion can make Oxygen sensors extremely difficult to remove. Why not try to loosen the sensor before you go off to buy the new part? If you can get it to turn at all, it’ll almost certainly come off. If you can get it loose, tighten it back up temporarily, then go find the replacement. If you can’t break it loose, pay a mechanic – who probably has a better set of tools and more experience with O2 sensors – to do the replacement.

Any replacement that doesn’t turn the Check Engine Light on within a few starts will probably be fine. Barring the very rare error, the parts store list of replacement parts will list parts with the proper configuration for your car and you won’t have any trouble. It there is a problem, getting a replacement O2 sensor out to take it back won’t be difficult. It will not have been cooking itself into place for 15 years.

I took a long trip, mostly highway, and my gas milage was great as ever, 45 mpg. The guy at advanced auto hooked up the meter and told me it was the oxygen sensor. I didn’t see the meter. Then I decided to go to autozone, and he gave me a printout which states "catalyst system efficiency below thresshold-bank 1. Probable cause: air leak in exhaust before rear HO2S, AF sensor error, fuel system fault, faulty catalytic converter.