jbn
Member Since: 06 Jun 2017
Location: Hesse
Posts: 47
  
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| Disable Battery Back Up Sounder (BBUS) |
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Please bear with me: I know that this is not a new topic but after several searches over many days pulling together various pieces of information I have not been able to find an easy answer to exactly where the BBUS is located. Either it is so painfully obvious where it should be in the plenum in the engine compartment and mine was already removed, or I have totally missed the point. Such photos that I have seen posted are close ups only and do not show it in situ in context.
I am seeking to disconnect mine because bypassing the bonnet alarm sensor switch has failed to stop the alarm going off randomly, and yet at more or less the same time of day when it happens. Typically between 7-8 am, but it does not happen every day. This has been the case since at least a couple of years, but only periodically.
Having recently been reunited with my IIDTool I have checked all fault logs and there was nothing relevant, certainly no indications of the bonnet being open. I have cleared all faults and currently nothing is showing, but I will check again in 24 hours and again later next week.
As far as I can tell, the explanations for random alarm sounding are (in decreasing order of probability):
bonnet alarm sensor
BBUS / Anti Theft Alarm Siren
battery
For the battery, I have checked using the IIDTool and read the voltages as follows (external temperature around 25 C and about two hours after using the car); honestly I do not know if these are particularly good or bad values.
Battery = 13.5
Actuator supply = 13.3
Main engine control module supply = 13.2
I have owned the car for three years, and have no clear idea when the battery was last replaced but it has not shown any [other] problems until now. I should add that in the past couple of months the dashboard information display panel has often been corrupted but more recently appears to have settled down, though still capable of corruption from time to time.
Any and all suggestions on how to take this forward will be much appreciated; thank you.
EDIT: thought it should appear from my signature - LR3 HSE 2009 4.0 V6 petrol
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 4th Jul 2020 1:27 pm |
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aja4x4
Member Since: 14 Apr 2019
Location: Westbury
Posts: 2459
  
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If you disconnect the sounder the alarm will revert to the horn so it will still go off. Better to try and fix the reason the alarm is going off. Do you have a sunroof? The ultrasonic sensors could have got wet if the drain tubes are blocked.
You could try switching the ultrasonics off when setting the alarm to see if that helps.
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| 4th Jul 2020 1:53 pm |
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jbn
Member Since: 06 Jun 2017
Location: Hesse
Posts: 47
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Thank you, yet there is a sunroof but I routinely disable the movement alarm with the double press.
The motive for disconnecting the BBUS (and yes I know it will fall back to the horn) is that I read in some posts it can trigger if it loses the heartbeat over the LIN BUS:
Quote: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.
EDIT: correct CANBUS to LINBUS and other stupid typos 2009 LR3 HSE 4.0 V6 petrol
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| 4th Jul 2020 2:07 pm |
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