C250 CDi 2012 "Replace Key" message on dash

[Tonygw]

Hi Guy as per the title,

I changed the battery in my spare key which worked but now i get the error message "REPLACE KEY" when using that key. The original main key works fine.

The key with the problem still unlocks the car, starts the engine, everything works apart from that error message.

Do I really need a new key or can this one be reset?

Any advice appreciated thanks

 

[Tonygw]

anybody?

 

[Riva811]

anybody?

As per manual, you need a new key. With a process of elimination:
- Does other key work? Yes
- Did you replace the battery on that key?
- Did you perform a key reset?

 

[Tonygw]

Cheers, But I'm not one to blindly follow and on screen message from a computer LOL

Why would the key fail and whats wrong if it stillworks? This is what makes me wonder.

How do I do a key reset perhaps that might solve the issue. Mercededs want nearly £400 for a replacement key so there is no way I am going down that route.
An indepenedent lock smith want £200.. still a lot

I am sure there is away around this minor issue, anybody else have any ideas, much appreciated, thanks

 

[Skd884]

Use main key you may never require the spare, if you do it works fine.

 

[wongl]

Are you getting the replace key battery message as in this youtube video?

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[Tonygw]

No that's the funny thing it states Replace Key, not Replace key battery which is why I am confused..in the hand book it just says visit main dealer..

The key still seems to work fine. Cheers

 

[andy27168]

Hi,
Where did you get the new battery? did you look a the date on the battery packaging?
I was having issues with my key fob eating batteries, it turns out I was buying them from a local hardware store as they were only a pound each possibly less, the dates on the packaging was well out of date.
As the issue started with a battery replacement I would be looking to get a branded battery, or swap youre two fob batteries and see if you lose the warning or goes to the other fob, worth a try.

 

[Tonygw]

Cheers for the reply, The battery was bought from a reputable supermarket and is a good branded battery which came in a pack of two. I didn't check the date though, but certainly one works fine in my main key. Maybe I was unlucky and the other was not a good battery. I can only try another to see if that solves the issue.

Been quoted £200 for a replacement key from a reputable locksmith so willing to try anything LOL. Strange thing is that the key still works, locks unlocks and starts the car?

Cheers

 

[wongl]

Cheers for the reply, The battery was bought from a reputable supermarket and is a good branded battery which came in a pack of two. I didn't check the date though, but certainly one works fine in my main key. Maybe I was unlucky and the other was not a good battery. I can only try another to see if that solves the issue.

Been quoted £200 for a replacement key from a reputable locksmith so willing to try anything LOL. Strange thing is that the key still works, locks unlocks and starts the car?

Cheers

If you watch the video I posted in post #6, the car also starts despite the message. However after the battery was replaced, the message went away.

Given you have a pack of 5, a cheap solution would be to replace the battery with another one? Or better still, swap the battery in the spare key and see if the message 'follows' the key used?

 

[richard]

Suggest you try a Varta battery (from Amazon) : https://www.amazon.co.uk/Varta-CR20...8&sr=1-2-c8a51df4-6015-4603-b82a-8c2c24cf7e97