Before I get any smart commets, I know what the buttons do and how to start the car.

My question concerns the electronics inside the smart key for my 2002 CLK430.

I realize that the key uses both infared and RF, but when I start the car which is used?
It would seem the infared signal is used at some point durring the start up but is it used to turn the ignition on or just in the start position like in domestic vehicles?
If the infared is only used in the start position can any smart key turn the ignition on in my car?

Has anyone tried to manipulate the ignition circuitry for any mods?

 

My examination of the key is that there is two RF modes and an infrared mode. There are two power systems in the key. Battries operate the the long range RF and infrared when you push a button on the key. The key operates on AC power when you insert it into the ignition module. There are no contacts, but the primary of a transformer is in the dash, and the secondary is in the key. Induction carries the power into the key. The key then whispers on RF "I am a key." Then the ignition sends a light beam into the key that says "well, which key are you exactly?" The key then turns on its light beam and sends its serial number (which is permanent and unique to each key) and the secret handshake number which was agreeded on by the key and ignition on their last meeting. If the key is allowed by it's serial number and secret handshake, the ignition module will alert the car that the boss is "in the house." Then starting and driving can occur. If either of these things are not present, the ignition module turns on the imobilizer, and asks that the improper key wait outside. (behind the velvet rope, no doubt.)

No other key can start your car, open doors, windows, or trunk. Each authorized key can have separate settings for mirrors, seats, and wheel position.

The ignition module has places for eight keys. Each place can be programmed just once (no mulligans). If you lose a key, screw it up in the washing machine, or gets chewed by the dog, you have used a position. If all eight positions are programmed, and no key works......get out your checkbook. The module needs to be replaced, by a dealer. This is to initialize the new ignition module with your VIN, and that there is no foul play involved.

There is little room for mods in the ignition, beyond factory Keyless Go. Inside is a custom DSP, and there is no data published on how the IC works. Sindelfingen is trying their best to make sure your car remains yours.

 

Thanks for the colorful comentary.
I was hoping for a little more indepth technical on the insertion and turning of the key.
Possibly finding out if the RF signal was sent as the key was turned into the start position, but your explanation was soo entertaining it was a great start to a Monday.

 

An "in depth technical description" could constitute a security breach, right?

 

As far as I can discover, the key has a rolling code RF and IR transmitter, that is battery operated. Its most likely that both send out the same code but use a different, medium dependent, modulation method.

Next to this, there is a passive transponder. This is basically an RF-ID tag.

It works basically like Moviela describes, though, you should read "AC power" as "RF energy". The passive transponder is powered from this RF energy and reacts on it by sending its own unique number, usually a 64-bit code.

Robert.

 

RF energy would not produce enough current to illuminate the LED in the key that sends the pulse train to the ignition module.

It is a transformer that powers the active rf transmitter and infrared emitter when the Key is placed in the ignition. It is AC powered.

Take the battries out of the key and try it in the ignition. Like magic it still works!

 

The key gets its energy to unlock the ignition from an inductive coil in the collar that the key is inserted. The code stored in the key communicates back to the Security system (DAS3) over two redundant data lines and verified. The locking bolt is pulled out of the locking ring and secured and a signal is sent back to the electronic starter switch enabling it.
The electronic key will work in the ignition if the batteries in the remote are dead since that function is done by infrared/RF.
The codes are kept by MB via the vin of the vehicle there are three rails, when the vehicle is delivered key 1 and 2 and the emergency 3 are all on rail one which has 8 available spots, there is also rail 2 and 3 for replacement keys a maximum of 8 keys is possible up to 24 in its life. A additional key will move to position 4 a replacement will move to rail 2 or rail 3. Replacement keys will wipe the one it is replacing forever.
Properly coded keys from MB vehicle center can take up to 45 minutes to communicate with the vehicle, it will first not turn, and then not keep running untill the process is complete and the led will indicate the status, ON programming, OFF done, Flashing not ok.
Everyone understand, after 24, the computer, all the remotes, and a learning workshop key are required from MB and a new data base is created

 

if the RF part of the key should stop working but the IR and using the key for everything else (starting the car, etc) remains constant. is this a fault with the car's receiver or the key?

I'm asking because this has happened to my car, if anyone can help me out with this, ie where are the RF signals received in a W211 E270?