Assuming it's the Holden assist my step dad came up with the same conclusion after testing and research when he owned it. Now some of them do it some don't so I'm assuming it's an issue with the bcm or the assist unit. I know I can't unplug the assist unit as it ties into the security of the car. Do statesman and Caprice run same bcm or can I put the statesman bcm in and the assist won't be powered? Or do I find another Caprice bcm and assist set up? Another friend had the issue in his old boys same model and just replaced the bcm and it went away. This thing drains fast and is doing my head in. If you don't drive it everyday it goes flat.