95 Cavalier obc trouble codes

Where can I find a list of the numerical trouble codes , such as (12) and what the problem is , and how to correct that problem. Cavalier 2.2L . A friend read the code as a 12 , and told me that means the computer needs replaced, im not so sure of that. On rare occassions the car will crank but not turn over. If let it sit for about 45 minutes, it usually will start. Also the check engine light will come on Occassionally, and go off. It's been doing this for some time now, but the car seems to be running fine, except for the rare starting problem.

it should put out code 12 before any other codes. code 12 is not a real code, its more of a testing 1-2 testing 1-2. if it DOESNT display code 12 then you have a problem. read all codes after code 12.

[FONT=tahoma][SIZE=4]Thank you for your help, that's what I thought but wasnt sure. Do you know of a web site that lists the numberd codes and what the problems could be?