I'm sure many on this board know about the risk of signal amplifiers but I'll describe the problem anyway. Seems that these devices are easily available. The device receives the signal from your Keyless Go fob if it's within range (say in your house when your car is in the driveway) and amplifies it. The car thinks that your key is close by and allows the doors to be opened and the car driven away, no muss, no fuss, no alarm. Once the car is out of range of your fob it obviously can't be locked/unlocked or re-started but by then it's pretty much game over. I looked this problem up and came across the concept of the Faraday Cage. As long as you store your fob in a closed metal box (we use a metal bread bin), the signal is blocked and can't be captured and amplified.

Seems that MB may have recognized this issue because the fob on my '17 GLC has an "off" switch activated by double-clicking the lock button. The small LED on the fob stays on for a second to show that the key is off. I've tested this and it works like a charm. The manual says it's to conserve battery life (whatever you say guys). This doesn't help my wife and her GLK and she has to remember to put her key in the damn bread bin. Nagging to remind her is definitely not an option. I went to the dealer to see if we could get her key fob upgraded. The SA looked at me like I was a chimp quoting Shakespeare. He asked a couple of other people, gave me a verbal pat on the head and sent me on my way.

Dumb chimp question. In theory it should be possible to upgrade the circuitry on the fob but is it feasible? Not the most life-or-death issue on the board but if anyone has any ideas they would be appreciated.

 

I have done some work on identifying the signals from the fob with my spectrum analyzer just so I could get a handle on the risks of signal amplification. The keys have some pretty complex circuitry to receive signals from the door handles and the internal antennas at 125 Khz and and transmit to the ECU an encrypted identitiy signal at 300Mhz.

My cheapo solution was to buy a RF blocking bag from amazon for about $8. I can carry it in my pocket and drop the fob in it when I leave the car. I also have one at home and drop my keys in it when I'm home.

This accomplishes two objectives.
1. Blocks the signals so car can't be started by signal amp thieves
2. Makes sure the car goes to sleep when it's in the garage (If the car stays awake due to key being in close proximity to the key, it will draw 3- 5 amps continuously and drain both the car battery and the key fob battery.)

Note that there is a pretty good write-up on the Siemens Smart key system that Mercedes uses on Wikipedia under Smart Keys or Keyless Go.

It probably wouldn't hurt for people to start asking their dealers about the upgraded keys that you can switch off. Its a little more convenient than hauling the keys around in a bag. I'm betting most will get the same "deer in the headlights" look that you encountered when asking about the newer keys. If enough people start asking about it, maybe we can get some attention focused on the issue. Sounds like the signal amps are increasingly being used to steal cars and drive them away. Any car that uses the Siemens anti-theft system and most of the other competing solutions are at risk. At least one German auto organization found that almost all cars they tested were vulnerable.

My GLK is due for service next month and I'll see if my local stealership has a clue about the problem. Based on previous experience, I'm not holding out much hope.