Anti-theft alarm (page 3 of 3)

The anti-theft alarm LED is used as a visual deterrent, and is connected to the Alarm ECU (C57-4) by a pink wire. To illuminate the LED, the Alarm ECU provides a path to earth (C57-11) on a black wire. To extinguish the LED, the Alarm ECU provides it (C240-1) with a voltage equal to that provided by fuse 3 of the passenger compartment fuse box. As the potential difference across the LED is now 0 volts, the LED is extinguished. In this way the Alarm ECU can control the flashing sequence of the LED.

The Alarm ECU also controls the interior lamps. The ECU (C61-1) provides a feed to the both the front (C355-1) and rear (C356-1) interior lamps on purple/white wires. An earth is provided for both lamps on black wires.

The alarm system can be interrogated through the diagnostic socket (C40-8), which is connected to the Alarm ECU (C61-17) by an orange/light green wire.