Uhm... as written by adspru, my horn chirps at the second press, it doesn't "beep". I've never read anywhere in the manual about any beep, it's always mentioning the horn and it seems to give the same feedback, regardless of the presence of an active anti-theft system or not.
From the owner's guide:
Locking the doors
1. Press (lock) and release to lock all the doors. The turn signal lamps will illuminate. Note: The interior lamps will turn off [...] and the turn signal lamps will flash if all doors, trunk and hood (if equipped with active anti-theft system) are closed.
If the vehicle is not equipped with the active anti-theft system, the turn signal lamps will flash if all doors, trunk and hood are closed.
The parking lamps will illuminate.
This is already unclear to me... they're describing two use cases (active anti-theft system yes/no) but the behaviour is the same?? What is the difference between the two cases and why are they mentioning the difference at all?
2. Press and release again within three seconds to confirm that all the doors, trunk and hood are closed. Note: The doors will lock again, the horn will chirp once and the turn signal lamps will flash once more.
If any of the doors, trunk or hood (if equipped with active anti-theft system) are not properly closed the horn will make two quick chirps and the turn signal lamps will not flash. If the vehicle is not equipped with the active anti-theft system, the horn will make two quick chirps and the turn signal lamps will not flash if either door or the trunk are not closed.
Here, at least, there's a difference between the alarm/no alarm options: the hood is not counted in the second case.
But once again the light/horn sequence is the same
I also went through the section of the active anti-theft system, but there's nothing about the locking procedure there. It's only saying that the alarm will be armed 20 seconds after locking the car, regardless of which button you press and how many times...
Arming the (active anti-theft) system
When armed, the active anti-theft system is designed to notify you of an unauthorized entry. When unauthorized entry or towing occurs, the system will flash the turn signal lamps and interior lamps and will sound the horn. The system is ready to arm whenever the key is out of the ignition.
Any of the following actions will arm the alarm system:
• Press the (lock) control on the remote entry transmitter portion of your integrated keyhead transmitter.
• Lock all doors using the interior power lock switch while the driver or passenger door is open and then becomes closed.
• Lock the driver door with the key in the key lock cylinder (this will not however arm the interior motion or vehicle incline sensing systems).
There is a 20 second countdown when any of the above actions occur before the vehicle becomes armed.
Each door, the hood or the trunk is armed individually, and if any are open, they must be closed for the system to enter the 20 second countdown.
The turn signal lamps will flash once when all doors, the hood and the trunk are closed indicating the vehicle is locked and entering the 20 second countdown. If any closure is not properly closed the turn signal lamps will not flash and that closure will not be armed.
I'm still confused
It seems that pressing twice is totally useless... and since it's making un-necessary noise at night, I would gladly avoid it if it's not needed.