Check Engine Light-01 Z24 Cavalier-Can't read codes!

[fulltilt06]

I have a 2001 Chevy Cavalier Z24 with the 2.4 liter engine.
The check engine light came on about a month ago, so I took it to my local Autozone (twice) to get them to read the codes.

The first time, the girl was getting ready to go to break when I asked her to check the codes, so when she plugged it into the car and said "it's not working"....i figured she was just in a hurry to go on break.

So, I took it back about three days later and asked another person to check my codes. He plugged the machine into the connector under the dash and it did NOTHING! What the hell!?!

My questions are....."If the code reader does not read any codes: Is my computer shot? How am I supposed to fix something if the diagnostic machine cannot tell me what it is? I have not been able to find any info on testing the individual engine-management sensors, so i'm at a loss as to what to do next.
I'm leaning toward replacing the computer. Any help would be greatly appreciated. Oh yeah, I tried unhooking the battery to reset the "engine light"....it didn't work either. If anyone has any ideas please email me at [email protected] or respond here. A BIG THANKS in advance for any help!