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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9 Responses to F10 rear trunk button and light

  1. Treber says:

    I know this is an old post, but how did you fix the issue? I have the same problem and was wondering.

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  2. Edvinas says:

    Same problem. Thnx for your thread, it helped me a lot. Replaced latch and trunk works propertly again.

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  3. Kirk says:

    Hi, I am also having the same issue. The trunk’s light did not work.
    Do you mean in order for the trunk’s light to be grounded, you will have to replace the trunk’s latch?

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    • 80% of the problem is the rear trunk latch,,,the rear trunk light gets its ground signal when the latch opens up,,,,you could have another issue with the rear trunk harness,,,,what you need to do is see if the rear trunk light is getting power and ground signals,,,it should have power all the time.,,and once it gets ground signal it will light up

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      • Kirk says:

        Hi BMW Technician,
        Thank you very much.I have checked the fuse 154 to the trunk’s light’s +VE connection and ground connection. The connection to the ground is definitely open circuit. It might be the harness as you have mentioned. I will also check for the trunk latch just in case it needs the complete trunk latch’s to be replaced. Will be in touch. Best Regards,Kirk

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