You guys have helped me in the past with this car. I hope you can do it again… My fiance owns a 2002 Chevy Cavalier with a 2.2 OHV Engine. It’s been more than a year ago now that I replaced the head gasket and about six months ago that I replaced the fuel pump and fuel filter. This past month the check engine light started coming on after driving on the interstate for more than 10 minutes or when we turn the A/C on. When this first happened, the engine temp went a little higher than normal so I drained the coolant and replaced the thermostat. If we let it rest for a day, the light usually goes off. I also noticed that when the light first came on while driving at about 65 mph, it seemed to lose a little power on acceleration. At one point I thought I smelled coolant, but it only happened once and when I check there seems to be no loss in coolant even after the engine has cooled. I’ve changed the oil and there was no coolant in it. The spark plugs and wires are new. We did take it on a 2000+ mile trip two months ago, but there were no problems until a month ago. Is there anything else I can check or do I need to make the investment on a code reader? If I do need a code reader, what kind would be good for this car? Keep in mind, I am in the medical profession and have no formal mechanic training. I have only been able to fix what I have so far by extensively researching. Any input would be greatly appreciated.
If you can pull the code, you can research probable causes for the code being set and probably fix the problem. It may be completely unrelated to what you are currently suspecting. If you live somewhere other than California, you can take the car to a chain auto parts store like Advance or AutoZone and they will read the codes for you for free. Once you have the code number (like P0123 or whatever, ignore the plain English description), you can post it here for our perspective and/or do some more research to find probable causes. Anything that happens at the auto parts store after finding out the code number can and should be ignored. They are in the business of selling parts, and this is a sales tactic, but can be very useful to you as long as you do not buy into their sales pitch. Often, they will tell you “this code means replace this part” and they are wrong. The code will put you in the ballpark of a diagnosis, but no code ever means replace a specific part. Let us know what you find out.
Thanks. I would have never thought of getting it read there. But now I don’t have an excuse to buy a new toy 
If all you want to do is read the codes and you want to buy one any basic/cheap OBD II code reader will work on any car '96 and newer.
While you are getting the code read, pick up a new radiator cap. You have the classic symptoms of low pressure in the cooling system.
I’ll see what Autozone has to say first. If they get too pushy, I’ll pick up a cheap one. Thanks.
While at Autozone, borrow their code reader. It won’t cost anything. They hold a credit card while you use the reader. Then they print out the codes for you and return the credit card.
After you drained the coolant, did you refill it?
FYI you can pick up cheap code readers on ebay for well under $50.
Yes. I did refill it.
I found a code reader online that actually hooks up to your laptop for 60 bucks.
The light hasn’t come on in a while so I haven’t taken it in to autozone yet. I live in the midwest and it’s heating up here so I’m sure my fiance will be unable to resist the temptation of th A/C. I’ll be bringing it in soon.
When the light comes on, the code is stored until cleared. The light doesn’t have to be on to read the trouble code. Sometimes they will clear themselves if there is no repeat in X miles or X key strokes.
Oh. Good to know. I’ll get it to autozone on my next day off. Thanks.
Some of the readers display live data but if you have an interface for a laptop it must offer even more access to the data stream. I would imagine it is well worth $60. If you get it please update us on how helpful it is.
Sorry it took me so long. I forgot my login info… I went to the auto parts store and they read the code P0130. It was the upstream O2 sensor. An easy 40 dollar fix. Thanks for the help.