Ford 1996 Crown Victoria Manual page 120

5. Five seconds after you press the fifth digit,
your door lock system will lock and unlock
the vehicle doors to confirm successful
programming.
The keyless entry system registers this
second code. To open your vehicle, you can
now use either code. The module remembers
only one personal code at a time. Entering a
second personal code will erase the first,
replacing it with the new second one.
To erase your personal code:
1. Enter the original permanent code.
2. Press and release 1/2 within five seconds of
Step 1.
3. Press the 1/2 button a second time and hold
for two seconds.
The keyless entry system automatically
erases your personal code. The system will
now only respond to the permanent code.
Do not set a code that presents the numbers in
sequential order, such as 1/2, 3/4, 5/6, 7/8, 9/0.
Studies show that people who idly press the
buttons usually press a sequential pattern. Also,
do not select a code that uses the same button
five times. Thieves can easily figure out these
types of codes.
Your door lock system will lock and unlock the
vehicle doors to confirm successful erasure. The
system will now only respond to the permanent
code.
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