So my car didn't pass smog, and I need to replace the oxygen sensor. I'm unsure what to buy though. I was told not get an cheap aftermarket sensor, but I'm not sure where to get a good one.

Can someone please enlighten me as to where I can find the right sensor and what is best? :)

Welcome to AF. Bosch replacement sensors will do the job, Napa, Autozone they all carry the right stuff. The how to can be found at autozone.com, repair guides, register and go to engine controls and emissions for your car. Or GM oe if you prefer.

NAPA or GM are your best bets

So I bought my sensor from a Chevy dealer, and it's the right part.
Now I need help locating the old one so I can replace it. They gave me this diagram, but I can't really understand what it is because there is no labels (just numbers). Can you help me find my O2 sensor on the car?

http://img36.imageshack.us/img36/1559/img0470i.jpg

Look down in between the engine and the fire wall. You will see the upstream O2 sitting in the top of the exhaust manifold. You'll need a 7/8 wrench or an O2 Socket to get it out. The sockets work the best on these engines.

BTW, #8 is the O2 sensor on your diagram.

Thanks! I'm pretty sure I found it. I replaced the part so I'm 99% sure it was right. This is an old oxygen sensor, right?

http://img204.imageshack.us/img204/2517/img0471u.jpg

EDIT: Yeah it was between the engine and the firewall, on the drivers side. it took some poking to find it though. if anyone else needs help as I did, Look for the black 4 pin connector that sits higher up near the hood, and then follow it down to the sensor.

Bosch oxygen sensors are junk and I have seen them fail.I do not trust anything Bosch makes.

That's odd, since Bosch was the OEM supplier for GM for many, many years.

The company I used to work for (Textron) made various sensors for GM and Ford, and always rolled the GM/Ford logos and part numbers into the shells for identification. They made spark plug shells, PCV valves, and all sorts of other "OEM" parts for the OEMs, including Honda and BMW.

I have yet to have an issue with a Bosch O2 sensor as well. It's all we use except for the rare occasion we actually install an O.E. part.

Bosch makes Carquest's oxygen sensors and I have seen a couple of them fail.Sent them back as defective and now get them from a Parts plus parts store made by Standard which have held up.If it is made by Bosch: JUNK!