[bour]

"I disconnected my battery while installing a Stereo in my 2003 Ford Mustang GT,as a result, the doors do not lock automatically right after driving off. How do i fix this ?"

 

[gaven60]

Probably need reprogramming. Your owners manual should have the info. I don't have a copy, so this is the best I can do, the dealer might be able to tell you over the phone, though

 

[aronek]

Check the owner's manual. Some newer cars can be reprogrammed to do things differently.