I bought a 2001 Mustang GT Convertible on Friday. It ran pretty good just had a few minor issues. I parked it on Friday at my house and disconnected the battery because it wasn't holding a charge and left it. Today I go to start it and and it just cranks but doesn't fire up, the "THEFT" light is blinking when I'm turning the key. What could the issue be? On Friday I turned it on and off about 4 times and no issues but today nothing. Just cranks and doesn't start.