How can you find a check engine code on a 05 Challenger without Candoo system?

[Kvg20]

I just bought the two oil sensors for my challenger because I was getting a oil light and a long beep while out on the water. I changed the Ops sensor on the crank but I couldn't break free the one on the oil tank. Frozen solid, so I'm just waiting for a buddy of mine to give me the right socket, all i had was a wrench. Being I'm in jersey this past weekend I had to winterize it do to the weather. While I was winterizing it I got a check engine light. It didn't come on right away but I have a feeling it has to do with me messing with the Tops. Is there anyway to find out what code its throwing without the Candoo program? Can I count the beeps to tell me what code it is? I know this will be hard as the motor needs to be running for the light to come on but maybe it could've stored the code. Thanks