How to switch off key transponder signal.

[jack-s]

Sorry if this is in wrong section, I'm not a regular. Problem. ..New C class 1 week old today. I can't switch off either of the keys with a double press of lock button to prevent the transponder code being grabbed for keyless entry as I could with the keys of the E Class I traded in. I've found various suggestions on the internet but none work. I've found a talk through of the latest C class uploaded by a Mercedes Dealer and they show the double press on exactly the same looking key as mine and with the same vehicle which, with a double press, gets the long flash and shuts down the key preventing the tranponder signal from being transmitted and also saving on key battery by shutting down the movement sensor. Grateful for any ideas or suggestions please 'cos I'm out of them. ...Thanks

 

[mioba]

If a brand new car - take a trip to the dealer. could be a programming issue.

 

[Srdl]

If it’s brand new, nothing to worry about. Since mid 2018, Mercedes keys have motion sensors built in so they stop transmitting automatically when they are stationary (on a hook, in a drawer etc). I tested mine sometime ago and the car wouldn’t open with the key next to it on a shelf

 

[jack-s]

If a brand new car - take a trip to the dealer. could be a programming issue.

Thanks Mioba, I did that today, went to their local MB Service Service Centre (different location to the MB Sales place) They said try xyz, it didn't work, they said try zxy, that also didn't work, they said try ... I said you come to the care and show me. They did and tried various combinations, then went away to scatch their heads only to return and say manual isolation doesn't work with that type of key it has a motion sensor which puts the key to sleep, which I know and had already made them aware I knew that. Fortunately one of their motor trade customers overheard the conversation. (He was there collecting some body work parts and decided to get himself a coffee while waiting) coincidently he was driving a new 2023 C class just a few months older than mine with exactly the same key and he was able to show them that a double press did get the long flash on the key and did switch the key off. They then said leave my phone number and we'll make enquiries and contact you. But I somehow get the feeling I might have be a long wait.

 

[jack-s]

If it’s brand new, nothing to worry about. Since mid 2018, Mercedes keys have motion sensors built in so they stop transmitting automatically when they are stationary (on a hook, in a drawer etc). I tested mine sometime ago and the car wouldn’t open with the key next to it on a shelf

Thanks yes I know, The motion sensors are working on both new keys but not the manual switch off. A couple of MB Main agents have uploaded videos on Youtube showing the double click on the latest keys to switch them off. One of them using a 2023 spec C class same as mine to demonstrat how the double push switches the key off to save battery and prevent signal grab when the key can't be stationary. My issue is that keyless entry itself is not a security issue it's the keys transponder signal that is the problem which is transmitted while the key isn't stationary, like while in your pocket etc. ... Senario, You are visiting friends, you are in their front lounge at night with the window blinds closed, your new Benz is parked outside and the key is in your pocket merrily sending out transponder signals for any signal grabber to pick up. Keyless-entry is car based and not an issue. Even with Keyless entry completely disabled with the transponder signal they can still open the doors just as you can by pressing open on the key and then start the car with the same grabbed signal. The other thing about not being able to switch the key off manually is that the key will still be using battery to run the motion sensor and the new keys are rechargable so if, at some point, you need your spare key there is a chance the motion sensor will have flattened the battery just when you need it. I undrstand that the new keys are recharged by placing them on the induction charging pad specifically for the key found in the centre console with an outline of a key on it. So if the car is locked and the battery in the spare key is flat ??? Although I guess it's then mechanical emergency key fiddling time and a wait with fingers crossed for the key's battery to get some charge before it will start.

 

[jack-s]

Taken a while but have found the answer. It is in the handbook but it's war and peace as you will know. It advises switching off the key when not in use for long periods. But there is also the situation mentioned above to consider. It seems the function of this very latest key has changed even though it looks the same as earlier 2023 keys.

You press and hold the lock button then with your other hand immeadiately press the open button twice quickly. You will get the long flash on the red LED to show the key has been shut down same as the last gen. of Merc. keys. You have to be quick though, if you leave it more than a second after pressing the lock button it doesn't work. I never do this in a car park though as that is the best thing about keyless entry. Anybody watching you park up with a code grabber can't grab the signal as the Keyless signal is of too short a range. Unlike when the remote key is pressed which flings the code out all over the car park.

 

[Srdl]

Well done - you just need to change your profile now to show your new car not the E220

 

[malcolm E53 AMG]

Thanks for this I hadn’t realised switching off the key not in use for a long period also extended the key battery life - I know I should have read the manual thoroughly like we all do lol

 

[DSK]

Manuals for modern cars should all be official videos online on the manufacturer website. No one is going to read hundreds of pages of car manual.


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