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Mercedes M Klasse Key Battery Warning

My 2003 Mercedes M Klasse with a gasoline engine is throwing a 'Key Battery Low' warning. It's got 254992 km on the clock. Keyless entry is completely dead now, and there's an error code stored. Sometimes it struggles to lock or unlock. Pretty sure it's just the car key battery, right? Anyone else had this happen with their auto key?

4 comment(s)

Sounds familiar. I had similar issues with my old C-Class. The low battery warning is usually spot on. Key fob range gets terrible, then keyless goes kaput. Have you tried the spare key to see if that works normally? That'd confirm it's definitely the battery replacement in the key fob.

Good call on the spare! I forgot all about it. Just tried it, and it works perfectly. So, definitely points to a low battery in the main car key. Is it a pain to do the battery replacement myself, or am I better off just taking it somewhere?

Okay, so definitely the battery. Battery replacement is easy enough if you're careful, but those little batteries can be fiddly. Plus, some keys can be a pain to open without damaging them. Honestly, for the price of a new battery and the potential hassle, it might be worth having a professional handle it. You don't want to damage the key fob. It's up to you though.

Appreciate the advice! I decided to just swing by a local shop. 37€ later, and it's all sorted with a new battery. No more error messages, and keyless entry is back. Thanks for confirming my suspicion – saved me a lot of time messing around!

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