Check-engine light for no apparent reason
 

Just got the car Sunday and it threw the light this morning. Drove it about 50 miles or so Sunday, it sat yesterday and this morning i started it to move it in the driveway, then backed it in and turned it off. Wife got in and started it and the light came on. Needless to say, Im super pissed that the light came on after having it only 2 days. Wife says that its running and driving fine, so I'm hoping that this is a small sensor code or something. Are there common codes these things throw that I should look out for?

I'm planning to take it to AutoZone this evening to get the code read. They can do that with the OBDII reader right?