Never mind, although the car is now gone I was still curious so payed the 24 hour access fee to bmw tis.

As I thought, exposed wiring going into left hand side tailgate at site of rubber grommet. The defect is very small and just needs insulating tape to fix.

I can post PDF if it will help someone else, just not at moment as on my ipad.

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2009 135i M Sport Convertible
2008 X5 3.0si
2003 E46 318Ti M Sport Compact - donated to parents
2003 116i Hatchback - donated to brother
2002 316Ti - Sold
2000 318ci M Sport - Sold
1998 318i Sedan - Sold