Anti-Theft Alarm Operation (Description and operation) (page 2 of 6)

The BCU sounds the BBUS using a PO wire between BCU pin C0661-3 and the BBUS. In addition to sounding the BBUS when the alarm system has been triggered, armed and disarmed, the BCU can also sound the BBUS to produce mislock and EKA warnings. The BCU normally maintains a 12 volts power feed to the BBUS on the PO wire. To sound the BBUS the BCU disconnects the power feed.

Alarm sounder unit When fitted, and the IDM and the BCU determine that alarm sounder unit operation is required, the IDM provides an earth for the applicable relay coil in the passenger compartment fusebox. This energises the coil closing the relay contacts.

With the relay contacts closed, a feed from fuse 21 in the passenger compartment fusebox passes through the relay contacts and from the fusebox on a PB LHD/RU RHD wire, via header C0293 (RHD only), to the alarm sounder unit.

On LHD vehicles, the alarm sounder unit is connected to earth header C0552 on a B wire.

On RHD vehicles, the alarm sounder unit is connected, via header C0288, to earth header C0018 on a B wire.

Key in sensor A feed from fuse 20 in the passenger compartment fusebox is connected on a P wire to header C0289 LHD/C0294 RHD. From the header the feed is connected on a P wire to the key in sensor.

When the ignition key is inserted into the lock barrel the key in sensor contacts close. The feed passes through the sensor and is connected on a WP wire, via header C0293 LHD/C0289 RHD, to pin C0662-2 on the BCU.