I have a 2000 pontiac trans am. when i set my alarm my haedlight pop up. they never use to. replaced module,and headlight motors,still didn't fix it.

In your owners manual on pages 2-19 and 2-21 tells you how to change this.

Entering Programming Mode
1. Turn the ignition key to RUN, then to OFF. This will
disarm the content theft-deterrent/alarm system
(if equipped).
2. Remove the RADIO fuse. This fuse is located in the
main fuse block which is located on the left side of
your instrument panel. The radio fuse is on the lower
right-hand corner of your instrument panel. See
"Fuses and Circuit Breakers" in the Index.
3. Turn the ignition key from OFF to RUN three times
quickly (within five seconds). The vehicle will
respond by locking the doors, unlocking the driver's
door and releasing the hatch. Your transmitter is now
ready to match the vehicle. Leave the ignition
in RUN.
4. Press and hold the LOCK and UNLOCK buttons on
the first transmitter for 15 seconds. The vehicle will
respond as in Step 3.
5. Repeat Step 4 for the remaining transmitters.
6. When you have finished matching all of your
transmitters, replace the RADIO fuse.
7. Check that all transmitters work by pressing
the buttons.

Programmable Modes
Your vehicle can be programmed to one of the
following modes:
Mode 1: All Off (The headlamps will not flash and the
horn will not sound to provide you feedback that a
lock/unlock command has been received by the remote
keyless entry transmitter.)
Mode 2: Horn and Lamps/Lamps (Your horn will sound
briefly and your parking lamps will flash when you
press LOCK on the remote keyless entry transmitter.
Only your parking lamps will flash when you press
UNLOCK.)
Mode 3: Horn and Lamps (Your horn will sound briefly
and your parking lamps will flash every time you push
LOCK or UNLOCK.)
Mode 4: Lamps (Your parking lamps will flash every
time you press LOCK or UNLOCK.)
Mode 5: Lamps/Horn and Lamps/Lamps (Your lamps
will flash upon the first press on LOCK, your lamps will
flash and your horn will sound upon the second press
on LOCK and your lamps will flash upon any press
on UNLOCK.)
Vehicles are delivered programmed in Mode 5.
To change the mode, do the following:
1. Press the UNLOCK button on the remote keyless
entry transmitter.
2. Count the number of chimes you hear. The number
of chimes tells you which mode your vehicle is
set for.
3. Press the UNLOCK button, again, on the remote
keyless entry transmitter until you hear the number
of chimes that correspond to the mode selection
you want.
The mode you selected is now set. You can either exit
the programming mode by following the instructions
later in this section or program the next feature available
on your vehicle.

When programming is complete, turn the ignition to
OFF and reinstall the RADIO fuse.