Ford Mustang Owner's Manual page 102

Battery Saver (With Remote Entry)
When the ignition is turned off, the vehicle will
turn off battery voltage to the interior lights
after 45 minutes.
This will prevent draining of the battery if those
lights have been left on inadvertently or if a
door is not completely closed. Battery voltage to
these lamps will be restored when the outside
front door handles are lifted, the Remote Entry
transmitter is used to unlock the doors, activate
the personal alarm or open the trunk, or the
ignition key is turned on again.
Replacing the Batteries
The remote is powered by two coin type
three-volt lithium 2016 batteries (included) that
should last for several years of normal use. If
you notice a significant decrease in operating
range, the batteries should be replaced.
Replacement batteries can be purchased at most
pharmacies, watch stores or at your Ford or
Lincoln-Mercury dealer.
NOTE: The operating range of the remote
entry system can also be affected by
weather conditions (such as very cold
temperatures) or structures around the
vehicle (buildings, other vehicles, radio
and TV towers, etc.). Typical operating
range will allow you to be up to 33
feet (10 meters) away from your
vehicle.
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