Had the same issue, replaced a negative cable with associated chipset.

what the tech told me was that main ecu was not shutting down because it was not receiving feedback from both sides of the battery.

i had a 9amp key off draw!

__________________

2007 4.8i X5 - Monaco Blue/Beige
Sport - Tech - Cold Weather - Rear Entertainment - 3rd Row Seats - Premium Sound - Rear Climate