Thread: Replacing O2 sensors

My check engine light came on awhile ago and I'm getting bad gas mileage. I don't have a code-reader or anything, but my hunch is a bad O2 sensor. Is replacing these sensors something that's easy to do yourself? I realize there's 2 or 3 of them and I'd likely have to replace them all. Or is it worthwhile to take it to the garage and have them scan it and charge me an arm-and-a leg. Any comments would be appreciated.

got an autozone by you?

Sorry, no autozone where I am.

Call around and find a place that reads codes and go from there. You should have partsource or something like that I think. Sometimes garages will do it free.

I would go get it scanned or pick up a $40 scanner from a local parts store... don’t want to go replacing things that don’t need to be replaced

Also you have 2 O2 sensors... the rear one (just behind the cat) is for emissions (and pretty much useless since it makes no PCM adjustments) the other (upper O2) is attached to your rear manifold... it reads and makes adjustments your fuel to air ratio... if this one is bad i suggest replacing it as soon as possible... mine went out, i ordered a new one but continued to drive it in the mean time... end result, the engine went lean and i bent up a rod

Hope this helps

CaStylin

They can be a pain to replace if its stuck. You can use a standard wrench or you can buy a special socket for it.

Thanks everyone. I think I'll pick up a scanner and go from there. At least if it is the O2 sensor I'll know to replace only the one on the rear manifold. I'm assuming that AC Delco is the most suitable brand of sensor for the Grand Prix. I've heard bad things about the Bosch ones ...

You would know if its the upper manifiold O2 if your MPG has been continuing to drop since the light came on.

The rear O2, although IMO usless, acts as a warning system and will still set a check engine light (Code P240)... and cause you to fail inspection in most citys/states

Find out which one it is an replace it... if you have a 00-03 then you can buy a o2 simulator for the rear one... its a little cheaper and if you ever get a downpipe then you have already gotten rid of the code that it will throw

Also... your are correct about the AC delco thing... go with the OEM... the bosch's are crap for most GM applications