Why will an unlocked Jaguar XF drain the battery faster than when it is locked?

I have a Jaguar XF 2.2 Diesel and keep it in a locked garage with the car unlocked. The service manager at my local Jaguar dealer told me there is less drain on the battery if the car is locked rather than left unlocked. Could you please tell me if he is correct and if so why?

Asked on 17 August 2013 by PB, St. Neots,

Answered by Honest John
He's right. The Bluetooth system will continuously search for the phone it is paired with. If you lock the car it won't.
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