Battery Drains When Engine is Off
 

I have a 2007 model with 45,000 miles on it. the other day, it wouldn't start so i jumped it and the radio said to enter the code. i didn't know what it was so i just turned the radio off. Now today, it wouldn't start again either. Is it because i didn't enter the code? or just a mechanical problem?

oh, and the horn started blaring the second i connected the jumper cables.

Check your grounds

Check the battery voltage with engine running to make sure the charging system is OK. (OK is about 13.5 to 14.5 volts) Next time you park overnight, disconnect the battery then reconnect it when you go to start again. If the battery still runs down by itself while disconnected from the car-- it is bad, you need a new battery.

You'll need to get the radio code from a dealer. It only stops the radio from working, it doesn't affect the rest of the car. The horn blaring was the stock alarm getting confused from lack of power.