2003 grand prix factory alarm

I have just installed a prostart into a 03 grand prix and the only item I am having trouble with is arming the factory alarm with the prostart keyfob. the only way I can arm it is with the original keyfob but when I remote start the vehicle it disarms and stays disarmed.  Is there any way to correct this or is this the only way to do it  in a grand prix. My 2002 sierra with the same system works fine, the remote start unlocks the doors starts the vehicle and then relocks the doors. Any advice would be appreciated. Thanks in advance.

i have the same issue with a 2003 rendezvous but i just notice today that the factory alarm arms itself after several minutes after i lock the car with the new key fob. On the factory fob i use to press the lock button twice to arm the factory system immediately and the horn honked, if you press the lock button once on the factory fob it will take a few minutes for it to arm automatically. SInce it arms automatically, you will see the factor LED blinking after few minutes, i am just going to leave mine alone, at least it arms passively, it should talk about in the car manual.