Perimetric alarm

Each time the handset button is pressed, the radio signal code is changed in a sequence mirrored by the receiver in the alarm ECU. If the sequence is broken, (e.g. by handset battery renewal, or by temporary vehicle battery disconnection, etc.), it will be necessary to restore synchronisation. This can be done by pressing the handset RH button four times in quick succession, until the vehicle responds by arming the alarm.

Perimetric alarm

The perimetric alarm can only be set using the handset. Each door, the bonnet and the luggage compartment incorporates a switch that closes as the aperture is opened. When a switch is closed, an earth signal is sent to the alarm ECU on a PW wire for the driver and passenger doors, on a PK wire for the boot and on a PR wire for the bonnet.

If a door is opened when the alarm is armed, the alarm ECU sends an earth on a PB wire to one side of the horn relay coil. Since the other side of the coil receives battery voltage on a P wire from fuse B6 in passenger compartment fuse box, the relay will energise causing the horn to sound. Once triggered, the horn will sound for a period of approximately 30 seconds - it can be silenced by pressing the plain button on the handset.

Engine immobilisation

The engine is immobilised when the perimetric alarm is set, inhibiting the engine primary electrical circuits. Immobilisation is removed when the LH handset button is pressed. The alarm ECU provides an earth on a WR wire (via the automatic inhibitor switch on a WLG wire in the case of vehicles fitted with an automatic gearbox) to one side of the starter relay coil. Since the other side of the coil is receiving battery voltage from fuse C8 the passenger compartment fuse box on a WR-WK wire, the relay is energised. Once this occurs, battery voltage is switched from link 4 in the engine compartment fuse box on an N wire via the MEMS relay module to the starter motor on an NR wire, with an immobilisation signal being sent to the MEMS ECM on a WS wire.