Operation (page 2 of 2)

The same principle is true of the LH door switch and the bonnet switch. The LH door switch (C033-1) is connected to the alarm ECU (C061-16) by a purple/blue wire, and the bonnet switch (C007-2) is connected to the alarm ECU (C061-9) by a orange/blue wire. The bonnet switch is earthed (C007-1) on a black wire. Both interact with the BBUS in exactly the same way as the RH door switch.

In addition to being supplied with a constant battery feed (C666-2), the BBUS also has its own internal power supply, and is earthed (C666-4) on a black wire.

The alarm ECU (C061-20) also provides a feed for the ultrasonic modules (C359-1 & C889-1) on black/brown wires. The modules are earthed (C359-2 & C889-2) on black wires. When the modules detect movement, they supply the alarm ECU (C061-3) with a short series of pulses on a white/black wire. Once the alarm ECU detects these pulses, the BBUS is again sounded.

To disarm the alarm system, the RF handset is used. The signal transmitted by the handset is received by the aerial. The aerial is connected to the alarm ECU (C061-26) by an orange/slate wire.

The anti-theft alarm LED is used as a visual deterrent and is connected to the alarm ECU (C057-4) by a pink wire. To illuminate the LED, the alarm ECU provides a path to earth (C057-11). To extinguish the LED, the ECU provides it (C240-1) with a voltage equal to that provided by fusible link 1. As the potential difference across the LED is now 0 volts, the LED is extinguished. In this way, the ECU can control the flashing sequence of the LED.

The alarm ECU also controls the interior lamps. The ECU (C061-1) provides a feed to the interior lamp unit (C357-1) on a purple/white wire. This informs the lamp unit to extinguish the interior lamps. When the interior lamp unit receives a reduced feed from the alarm ECU, it illuminates the interior lamps.

The alarm and immobilisation systems can be interrogated through the diagnostic socket (C040-8), which is connected to the alarm ECU (C061-17) by an orange/light green wire.