F10 rear trunk button and light

 Ok what a stupid picture,,,I know boring,,,,just want to show you something I learned today,,,F10 customer said the rear trunk will open from the key remote and the button inside the car,,,,but the rear trunk lid button won’t close the rear trunk and the rear trunk lights doesn’t work,,,,check faults none,,,I had no signal from the rear trunk lid button,,,I tried new trunk lid button still no signal,,, I checked the trunk lights,,,trunk light had 12 volts but no ground signal,,,,I saw the rear trunk area was repainted so I thought a damaged wiring harness,,,no luck,,,so next best thing find BMW wiring diagrams which suck sometime or they might be wrong sometime,,,,so I know there was no ground signal for the rear trunk lights,,,,so I trace the ground wire which gets spliced into the ground wire for the rear trunk button,,,then the wire goes to the rear trunk latch,,,,now the rear trunk latch has two ground wire,,,one is the main ground wire and the other is the activation ground wire when you open the rear trunk,,,,when you open the rear trunk the trunk latch grounds out the wire which activates the lights and sends a ground to the trunk button. So the rear trunk light and button share a common ground wire which come from the rear trunk latch once the trunk latch opens.

 

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