Alarm chirps twice upon locking and 3-4 times when

Check the battery

They only last 3 to 4 years in some cases
(cars battery)

That will make the chirp if the module voltage is low

Next would be to have the modules checked for codes
& or diagnosed to find a problem

reset the alarm follow the instruction and fix it.
God bless you

• 1
  Close all of your car doors.
  
  
• 2
  Insert one key in the door lock and cycle it to the "Lock" position, and then back to the "Unlock" position two times. Leave the key in the lock cylinder.
  
  
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• 3
  Enter your car and insert your key into the ignition cylinder.
  
  
• 4
  Cycle the key in the ignition from the "Off" position to the "On" position twice in a row. The alarm will emit a chirping sound after turning the ignition to the "On" position the second time. This will reset the alarm, making it ready for reprogramming (if necessary).
  
  

To turn off the auto locks 1 turn the key on 2 press the unlock button 3 times, 3 turn the key from on to off, 4 press the unlock button 3 times, 5 turn the key back to on and the horn will chirp, 6 press the unlock button, then the lock button. the horn will chirp once if the auto locks are deactivated, or twice one short and one long chirp if activated. 7 turn the key off and the horn will chirp once to confirm exiting the system

Contact a Pontiac Dealer, I believe on that van, if you take and cycle the key off and on 3 times, that will reset the alarm and anti theft thingy.

Does it have an aftermarket alarm. Most likely its either the aftermarket or stock alarm thats having the problem

IMPREZA: 2005, 2006, 2007 and
FORESTER: 2005, 2006, 2007, 2008
Check for Immobilizer key on Forester XT models only.
information is always subject to change and correction
new remote for 2005 Imprezas.
This is not the same remote as the 05 Legacy/Outback remote which also has truck/gate release on the front and a red panic button on the back.
Lock: press Lock button for 2 seconds or so to lock car, and arm optional security system. The car with chirp once and turn signals flash for locked, 5 short chirps and signal flashes if any door is not fully closed. The dome light goes on for 15 seconds and ignition key ring (if present) will light for 30 seconds when unlocked.
Unlock: press unlock one time for driver's door, press again within 5 seconds to unlock all doors inkling rear gate (wagon). The system does not open the trunk.
Panic mode: press and hold lock button for approx. 3-4 seconds to activate Panic mode. I panic model the horn honks and turn signals flash until either the lock or unlock button is pushed again.
Finder mode: Press lock button 3 times within 5 seconds to activate Vehicle Finder mode. The horn will honk once and the turn signals will flash 3 times
Distance: works within approx. 30 feet depending on battery strength, nearby concrete walls and etc.
Audible Chirp On-Off: the system will chirp when locked or unlocked. To turn OFF the chirps, unlock the door and then push both lock and unlock buttons at the exact same time for 2+ seconds. There will be 2 chirps indicating the the audible is off. To turn the chirp back on, repeat the process and the system will chirp one time when it is back on.
Battery: as the battery ages it will only work as you get closer to the car. When a battery is replaced, the transmitter must be re-synchronized with the Keyless control unit. To synchronize, press the lock or unlock button 6 times.
Programming: 4 codes may be programmed.
Sit in driver's seat and unlock all doors. Open and close the driver's door
Turn the ignition key from LOCK to ON position 10 times within 15 seconds. Be sure to stop at both lock and on. The horn will HONK once to indicate transmitter programming mode is activated. Leave key in LOCK position and don't remove it from ignition.
You now have 45 seconds to complete the programming as below.
Open and close driver's door again.
Push either lock or unlock button on the remote you want to program. The horn will honk 2 times when successful.
To continue and program other remotes at the same time: open and close the driver's door and push lock or unlock on the remote. The driver's door must be opened and closed between each remote you want to program.
Done programming? remove the key from the ignition and the horn will honk 3 times.
DELETE old codes? Reprogram 4 times, it will overwrite old codes.
Alarm Security System: optional on all models. When locked there is one chirp (can be turned off, see above), the turn signals will flash and the red 'security' light will start to flash once every 2 seconds except for STi which flashes twice every 2 seconds.
There will be 5 chirps if a door, hood, and trunk or gate is not fully closed
You can also arm the system by using the power lock button on the driver or passenger door as you get out of the car and then closing the door behind you.
Disarm the system: push unlock for 2 seconds
Lost remote, alarm activated? When you can't use a remote to turn off the system: open the door with a key or try to start the car and the horn will start to honk. Turn the key on-off 3 times within 5 seconds and the alarm will go off and you can start the car. It's simple!
VALET mode: To set valet mode or just to disable the security alarm system: 1. unlock all doors 2. physically open the driver's door 3. hold the UNLOCK button on remote for 2+ seconds. The red 'security' light will then flash 2 times a second until the car is turned on.
System has been Tripped (except for STi): if you unlock the door with the remote and it chirps the signal light flash 4 times, the system has been triggered;
Identification mode: To find out what happened and why the system was triggered:
Open and drivers door, leave it open. Turn ignition key from LOCK to ON 2 times and then leave in LOCK position.
Tripped code: 1 security light flash: a door has been opened, 3 flashes when the impact sensor was triggered, 4 flashes when the ignition was messed with or battery disconnected

some of those vans came with an anti-theft passlock system, it's a small chip in the key-- if equipped, the sensor in the ignition lock cylender failed alot with the early systems, with similar symptoms

The locking assembly in one or both of your doors has not been correctly re-connected.

sounds like it's in theft mode?
try using the fob to lock and unlock the doors 3X then open the drivers door with the key
if that does not work use the kill switch

Stand in front of the Van and press and hold both the lock and unlock buttons for 10 seconds.