I got a 2002 chevy s10 4.3 liter, I can listen to the radio etc fine while driving and if I have the key turned to the on position. But when my truck is shut off and I just turn the key to the accesory position just to listen to some tunes. My truck will beep beep, not a alarm sound. But the sound it makes when doors arnt always shut good, Ive checked all that but all the doors are always shut right. What is the problem of it makeing this beeping sound while its just turned to the accessory position?