IIRC its the flashing light near the gear stick (if this is on the V6?) that should flash in a pattern which relates to what sensor was triggered, the light will flash this pattern until the car is next started..
1 Blink: Doors, Bonnet, Boot Have been opened..
2 Blinks: Additional Sensor Triggered (something that probably don't effect you)
3 Blinks: Ultrasonic Volumetric Sensor Triggered (Internal sensor)
4 Blinks: Attempt To Start Car/Ignition
A common fault with the alarms was the internal sensor which was triggered by changes of temperature inside the car, more often it was heat being dispersed from the vents causing the alarm to go off, solution was removing the sensor from the pillars and changing the wires around making them less sensitive..
Hope some of this helps..