Mercedes Forum - Mercedes Benz Enthusiast Forums - Smart key(s) not working, car won't start, doors won't open

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- - Smart key(s) not working, car won't start, doors won't open (https://mercedesforum.com/forum/mercedes-c-class-10/smart-key-s-not-working-car-wont-start-doors-wont-open-33509/)

C240 2001

Since the weather turned cold recently my 2001 c240 has been giving me issues. When we have a cold morning neither of my Smart keys will open remotely lock or unlock the doors and then if I open the door manually(withmetal key) and insert the smart key into the iginition it will not allow me to turn the key to position 2. If i wait till temps warm up the smart key will unlock doors and then key will go to second position.
When this issue is happening all interior lights, radio etc DO work. Also to note, when vehicle is cold smart key DOES blink red light when attempting to lock or unlock. Car also does light redlight on shifter (P,R,N) when key is inserted into iginition, so to me that says it sort of acknologizes that it has been inserted but will not do the handshake to allow it to move to second position.
I have changed the battery,Replaced new Fuse box in the Truck(left side)I paid so far $800 and repair shop told me they can not do any thing more and no relay for the door.I wiil not buy any more MZB.

I know this sounds elementary but try putting new battery in smart key,,this just happened to me two weeks ago and i put a new battery in and it started working

I have changed battery in both keys.Nothing work but if I park the car in garage at night then I have no problems.

Same problem here..

I just got a new key from the dealership and it will unlock the doors then the lights will come on all nice and bright, but when I put the key in nothing happens. No "mechanical" noise and I can't turn the key to start. I recently had service done from a local non dealer shop who specializes in MB service. My wife told them about the key problem and they suggested a new key from a dealer, then they sprayed oil or something in the ignition and it worked fine until the next day and the problem started.. Before the no start issue it would take a few tries and then I could turn the key. '02 C240..

2001 C 240 door wouldn't open with smart key in the morning

I warm up the door lock and Antena above on the car with hair drayer,it did not work and let the car set until 10 am, the car doors open with smart key and all fuctions work.Next day I park the car in the garage all night and next day morning i have no problem to open the doors with smart key.now i start parking car in the garage.Is any one have answer about this issue?