Hi,
There is a way to reprogram the remotes. You do it with the key in the ignition and pressing a series of buttons within a certain time. Check your manual. If no luck search the forum and keep in mind your model year.

Joe

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2004 ML350 Black with charcoal leather, OEM Hitch, Rhino step, Bose, Navigation, OEM front guard, Comfort package, Entertainment package, Sunroof, heated seats.