I went to Autozone and they told me it was my O2 sensor. Will this affect my MPG? Is it OK to drive with this light on? It's so cold here with snow the whole bottom of my car is frozen. A friend told me it's an easy install. I guess the one on the bottom is bad for me. Also Autozone wants $100 or so for part. I was shown the very part on Amazon for $25. Do you recommend me using this part?

I just bought this car used and this light came on less than 24hrs of owning it.

 

It had probably been on previously and had been reset before you purchased the car. It's always a good idea to run a code check and see if everything checks out and shows in a ready state.
You can drive with it that way, but eventually you will destroy the cat. The car will run rich or lean depending on the reading the computer is getting.
You will want to replace it as soon as you can. Make sure you check the reviews on any sensor you buy. Some can be cheaper aftermarket, some need to be OEM. Depends on the sensor.

 

Yes, your mileage will be affected. Yes, you can drive with it on. I am sure you can find replacements on eBay for like $30. Just make sure the one you have has a harness to plug in, or you will be cutting and splicing wires under the car. The plug in type is a few dollars more, but makes the install MUCH easier.

I agree with Tigger... the previous owner must have reset the ECU before selling it to you and the monitors are now set, showing a CEL for the O2 sensor. Either that or it was completely random, which is unlikely. I have a feeling that the "good" code readers can tell you when the last time the ECU was reset, too

 

Exactly what number code is it?

1996 and later have two sensors. The first sensor (nearer the engine) is essential for proper mpg and performance. The second one (after the cat converter) is used only to confirm the operation of the cat. Thus you can ignore that unless you have to pass a smog test. (If smog tests are required, it is also sometimes a requirement that used car sellers have to get it tested and passed).

Also certain 1996 to 2000 models have a combined manifold / cat assembly which is prone to cracking near the first sensor. When that happens you can get a false sensor code (the real problem being much more expensive).

 

Thanks, guys. I also think the seller reset the light. When driving it he mentioned "Civic's run forever, usually when the check engine light comes on it's the oxygen sensor". Low and behold 13hrs later I get an engine light that's the sensor. I sent him a text right away calling him out.

The code that Autozone gave me was P0420...Paper below




I also purchased a bottle of Lucas injector cleaner and put in tank today. I filled it up the other day and have 119 miles on the tank and not at half yet.

 

https://www.google.com/search?q=erro...sm=93&ie=UTF-8

 

you should only use DENSO or NTK oxygen sensors in a honda.

 

Thanks! I will get a replacement soon.