Vehicle Security System Alarm Operation

WARNING: This page is about a different car, the 2006 Nissan Xterra. However, it is still accessible from the selected car via links, so may be relevant.

The vehicle security system is triggered by

opening a door
unlocking door without using the key or keyfob.
The vehicle security system will be triggered once the system is in armed phase,
when BCM receives a ground signal at terminals 12, 13, 47, 48 (door switch) or terminal 43 (back door switch).
When the vehicle security system is triggered, ground is supplied intermittently
from IPDM E/R CPU
to headlamp high relay and
from IPDM E/R terminal 45
to horn relay terminal 1.

The headlamps flash and the horn sounds intermittently.

The alarm automatically turns off after 50 seconds, but will reactivate if the vehicle is tampered with again.