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Phillip H
Phillip H, ASE Certified Technician
Category: Mercedes
Satisfied Customers: 515
Experience:  Vehicle Technician at Richmond Motor Services
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Second opinion] My Mercedes LED headlights no longer come on

Customer Question

second opinion] My Mercedes LED headlights no longer come on when I locked or unlocked the car and it was working fine before.
Submitted: 16 days ago.
Category: Mercedes
Expert:  Virtual-mod replied 15 days ago.

I've been working hard to find a Professional to assist you with your question, but sometimes finding the right Professional can take a little longer than expected.

I wonder whether you're ok with continuing to wait for an answer. If you are, please let me know and I will continue my search. If not, feel free to let me know and I will cancel this question for you.

Thank you!
Expert:  Phillip H replied 15 days ago.


You have stated that the LED Headlights no longer illuminate when Locking and Unlocking the Vehicle.  Are these the same Lamp Units that are used for the Dipped Beam Lighting on the vehicle?  If so then obviously the Lamps themselves work when using the Headlamp Switch.  Because of this I would be looking at one of the following:

  1. Communication issues between the Central Locking Module and the BCM (checked using Mercedes Diagnostic Equipment)

  2. Battery failure (low battery state of charge resulting in lamps not being illuminated ( requires battery testing using appropriate battery diagnostic equipment such as miditronics tester)).

If the Lamps are separate to the Headlamps and maybe mounted in the Bumper Area then potentially it could be a corrpded connector to the Lamp Units where the Bumper Harness joins the Engine Bay Harness.  It would be doubtful that two Lamp Units would have expired together hence checking the wiring first unless one had failed and you hadn't noticed it and the the other failed a while later in which case it may be the lamp units that are faulty.

You haven't provided any vehicle details so this is just general advice applicable to a range of vehicle.  If you have a Registration Number I can check to see if there are any wiring diagrams available to provide any further information.