You should be able to get an actual code off of the reader. Once you get the code you can find a website that will tell you what it means. Like this site. http://www.aa1car.com/trouble-codes/codes_699.htmFisherdude, I changed plugs about a month and a half ago. I actually swung by autozone today after work and asked the guy to plug in the diagnostic tool for me, which he didn't really care to do since the service engine soon light was not on at the moment, but tried anyway, and sure enough it threw out the lean bank 1 and lean bank 2 codes, or something along those lines( I didn't get a chance to write down the codes). The guy said that when it's just one of the codes I mentioned, it's the O2 sensor, but when it's both the codes I mentioned, it's mass air flow sensor. Does this sound right? I hate to spend $140 on a mass air flow sensor when that's not the problem. Thanks again.