W203 - both keys not working

[smurph1]

On my 2005 C220 Merc, both my keys fail to open car and work in ignition, any advice?
Note: red LED flashing on keys, and new battery in car a couple of months ago.

 

[Tinkerer]

I had this on one of my old cars after disconnecting the battery, had to get into the passenger door (pain!) and then play with the keys IIRC one in the ignition and the other just pressed to unlock ........ sorry can't remember for how long, just very frustrating. Hope this helps.

 

[Stratman]

Once you manage to break in, try resyncing the keys. It's in the owners handbook somewhere.

 

[Tinkerer]

Yeah sorry forgot to mention that, you get in using the metal key from the key fob, usually in the passenger door.