Hi all! I am new here and a new Mustang owner. Just purchased a 2006 4L V-6 with an auto trans. My problem is that if I unlock the driver's side door with the key the car will not start. It I umlock the door with the remote unlock the car will start. Is this a security system issue? What happens if the battery in the remote fails? Thanks in advance for all your answers.

 

i've never heard of this... lol

 

That's a new one. Time to bring it in for service...

 

It may have that dealership anti-theft system in it that the didn't remove. Sometimes dealers put them in the car and remove them at sale.

Either way go back to the dealer.