How to Replace the Key Battery for the New Mercedes-Benz ML420?

[VanLouis]

Slide open the tab at the rear end of the key to remove the mechanical key. Insert the mechanical key into the side slot of the key fob and press the internal gray button. With one hand, push the rear end of the key upward. When a gap appears, remove the mechanical key. Then use your hand to take out the rear end, and you can proceed to replace the battery.

[SanAngela]

Hi, I'm a long-time Mercedes owner and have changed key fob batteries several times. The newer ML420's smart key design usually has a small button or sliding groove on the back cover - pressing it allows easy opening. Remember to use a small screwdriver or key edge to carefully pry it open without excessive force to avoid scratching the plastic casing. The old battery (typically CR2032 model) removes easily, and replacements are available at local supermarkets or auto shops. When installing the new battery, ensure the positive side faces upward to prevent key malfunction. After battery replacement, snap the cover back gently and test lock/unlock functions. The entire process takes under 5 minutes, saving dealership service fees. Pro tip: Regularly check battery expiration dates to avoid aging issues. If it stops working suddenly, don't panic - reassembling might fix contact issues.