Tiburon Computer Codes

Is there anyway possible to read the computer codes myself? I keep getting a check engine light, and it started happening right after I put gas in it the other night. Car runs and sounds normal, no overheating or anything...although the oil appears sort of milky colored. Anyway, the only way to get the light off is to disconnect the battery, then it comes on again at some point. It's a 2001 and getting ready to turn 50,000 miles on it, just hoping that the light has something to do with an oxygen sensor or something because of bad gas...

Cap is tight and I added octane booster and unplugged the battery, but then the light comes on eventually again.

if the cap was left loose and the cel came on, it will take about 5 driving cycles for it to dissapear once tightened.

for reading codes, you can go to autozone and they will do it for free. or you coould buy a cheapo code reader off ebay.