Ford Mustang Owner's Manual page 220

Driving
If you cannot move the gearshift lever out of P (Park) with ignition in
the on position and the brake pedal pressed:
1. Apply the parking brake.
2. Using a flat head screwdriver or
similar tool, remove the cap.
3. Locate the access hole at the
front of the area under the cover.
4. Insert the screwdriver or similar
tool into the hole and press and
hold the lever forward while pulling
the gearshift lever out of the P
(Park) position and into the N
(Neutral) position.
5. Reinstall the cap.
6. Start the vehicle.
If it is necessary to use the above procedure to move the gearshift lever,
it is possible that a fuse has blown or the vehicle's brake lamps are not
operating properly. Refer to Fuses and relays in the Roadside
Emergencies chapter.
WARNING: Do not drive your vehicle until you verify that the
brakelamps are working.
WARNING: When doing this procedure, you will be taking the
vehicle out of park which means the vehicle can roll freely. To
avoid unwanted vehicle movement, always fully set the parking brake
prior to doing this procedure. Use wheel chocks if appropriate.
WARNING: If the parking brake is fully released, but the brake
warning lamp remains illuminated, the brakes may not be
working properly. Contact your authorized dealer as soon as possible to
have the system serviced immediately.
220
2012 05+ Mustang (197)
Owners Guide, 3rd Printing
USA (fus)