LR3/Disco 3
The BBUS is attached to the plenum in the engine compartment, next to the brake booster. The BBUS uses an integral
sounder to produce the audio warning after an alarm has been triggered. In some markets, a tilt sensor is incorporated
into the BBUS. Externally, the two types of BBUS look the same.
Operation of the BBUS is controlled by the CJB. The CJB and the BBUS exchange signals over a Local Interconnect
Network (LIN) bus communications link. The BBUS is normally powered by a permanent battery power supply from the
CJB. An integral rechargeable battery powers the sounder if the power feed is disrupted.
When it arms the anti-theft alarm system, in the perimeter mode or the volumetric mode, the CJB sends an arming signal
to the sounder in the BBUS. When it arms the anti-theft alarm system in the volumetric mode, if a tilt sensor is fitted, the
CJB also sends an arming signal to the tilt sensor. On receipt of the arming signals, the sounder and the tilt sensor
respond with a status signal. If there is no response to the arming signals within 12 seconds, the CJB assumes there is a
fault and sends a disarm signal to the sounder or the tilt sensor, as appropriate. The CJB also stores a related fault code.
When the sounder is disarmed, while the anti-theft alarm system is armed, if the alarm is subsequently triggered the CJB
uses the horns to sound the audio warning instead of the sounder.
While the sounder is armed, the CJB sends a periodic signal (heartbeat) to the BBUS, and the BBUS monitors the battery
power supply and the communications link with the CJB. The BBUS operates the sounder if:
It receives an alarm signal from the CJB or the tilt sensor.
The power supply or the communications link from the CJB is disrupted.
The tilt sensor measures the longitudinal and lateral angle of the vehicle over a range of ±16° from the horizontal. When
the anti-theft alarm system is armed in the volumetric mode, the BBUS stores the current angles in memory and monitors
the tilt sensor readings. If the vehicle attitude changes in either direction by more than the alarm limit, the BBUS activates
the sounder.
VOLUMETRIC SENSOR (WHERE FITTED)
Item Part Number
Description
1
-
Front transmitter/receiver pair
