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2006-2009 Range Rover Sport
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Discussion Starter #1
This morning I went to open the car and it wouldn't unlock. I went inside to get the other key, I thought the key had a flat battery,and 5 mins later the car started alarming. I went back to the car, it was unlocked, so I jumped in and press the start button and the alarm stopped and it started. The clock had stopped and the automatic windows wouldn't wind up automatically so I had to reset them. Its like the battery went flat through the night, yet I could start it .Could someone please tell me what happened there, very strange
 

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You likely are experiencing a situation where the battery is discharging either through a drain, or through a defective battery. Essentially, the BCM checks the battery voltage constantly every few minutes. If the voltage drops below a certain voltage, the BCM will disconnect the battery from the vehicle, essentially isolating it from the vehicle. This preserves battery capacity until you signal the system, through your key sender that you are ready to use the vehicle. The BCM will then re-engage the battery with the vehicle, where the vehicle will need to go through a reset. This may include alarming the vehicle, and re-energizing the entire vehicle. This will also require every module to go through a self-check before entering its normal operation modes. Ray
 
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