I believe this function is taken care of by the door lock pump/module as its also a rudimentary signal aquisition module for the rear of the car. You said that the battery area was wet, the pump module sits right there.

but i dont think any interior lamp failure is displayed in the dash screen, its exclusively for the outside of the car. Check the little orange marker lights on the front bumper, they will also trigger that.

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2012 BMW X5 (Beef + Granite suspension model)

1995 E300D - The original humming machine (consumed by Flood 2017)
2000 E320 - The evolution (consumed by flood 2017)