erik_dragon3

Mercedes S Klasse Key Battery Warning

My 2009 Mercedes S Klasse diesel is throwing a 'key battery low' warning. Keyless entry is dead, the error memory logged the issue, and I'm struggling to lock and unlock the car. Is this a dead key situation? I suspect the fob battery is the culprit, but what else could it be?

4 comment(s)

Sounds familiar. I had similar electronic key issues with my S Klasse too. Is the key fob battery truly low? Have you tried replacing the battery in the key fob?

I haven't replaced it yet, should I replace it first before getting it checked?

That's the first thing I'd try. It's almost certainly the low battery and it's by far the cheapest fix. Otherwise, you may need to go to a workshop to get the key reprogrammed or replaced.

You were spot on! Replaced the fob battery, cost me 37€, and everything's back to normal. Keyless entry works, and the error is gone. Thanks for the advice!

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