I have a 2003 MB c320 with the original key. The key is able to start the car perfectly fine, but when it comes to using the remote buttons, nothing works.

When I try pressing the lock, unlock or open trunk buttons, the car doesn't react, and I know the key has batteries because the red LED flashes every time I press them. I thought maybe the key isn't programmed properly to the car anymore, but then it shouldn't be able to start it either right?

Is there anyway I can reprogram, reinitialize or reset the key so that the buttons would actually work? I know I can bring the car to the dealer, but I don't think it's worth spending all that money to get another key with working buttons.

If it helps, the rear window and the rear passenger windows are factory tinted and we also have a w203 replacement key (the buttons on that one aren't working either).

Any help is appreciated!

  • 2
    I'm pretty sure the Mercedes keys are the type which can only be dealt with at the dealerships, but you could possibly check with a key/safe/lock place and see if they know differently. Commented Jul 4, 2016 at 14:43

1 Answer 1


I have just had a Mercedes Key that would not unlock the doors but would start the Vehicle. So I sent it to a specialist car key doctor This is what he found.

Check out Mercedes Smart Key, find damaged casing and switches and bad connections. Remove all switches and fit 3 new switches, redo bad connections, fit 2 new batteries and test, key working but appears to be draining batteries. Investigate further and find key is transmitting continuously in infra red circuit. Trace fault to defective controller chip, replace and retest, key is working well, batteries are not draining anymore. Fit circuit board into new casing.

So there are firms out there who specialize in key repairs Cheers

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