Upgrading to a Chrome Key

wardpaa

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Wondering if anyone with an electronics background can offer any advice on why my new chrome key does not operate the immobliser on my 2005 CLK.
To briefly explain the situation, I have purchased a Chrome 3 button key off of Ebay with the intention of swapping the chip out of my old cracked key into the chrome one. The seller sells one of these keys a day and they are practically new.

After transfering the chip, the chrome key now does everything (IR and RF) to Lock/Unlock the car, remote windows, BUT, will not let me turn the EIS when inserted.
I have verified IR being transmitted from the EIS when the key is inserted but the key appears to be ignoring it - or could it be more work needs to be done ?
The donor key was working before I transfered the chip and I have a second cracked older style key that is fully operational -or i'd be stuffed.
I have tried swapping coils over, measured resistances etc, checked connections from every pin on the chip to where the track goes, shorts etc, but all OK.
Any teckies on here that know how these keys work and if a key previously programmed to another car needs more than one chip/components transfered or maybe a re-sync using software ?

PS
This all started on a thread on another site:
http://www.mbclub.co.uk/forums/electronics/74824-reprogramming-w208-keys.html
 
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television

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The key is in 3 parts,,the locking both RF and IR these run from the internal batteries within the key. When the key is in the ignition it is powered from the transponder coil, and does not use the internal batteries. In the picture you can see the transponder energizing coil that can fail on the key

The front half of the key is the section devoted to the ignition section from where the PCB tapers inwards.

To see and test the key you can insert the key into the ignition and if it will not start,,press any button on the remote while it is in the ignition,,this should enable you to start the car and would prove the the fault is within the coil on the tapered part of the PCB

The other comments made in the link are not quite correct, it is the same PCB for a 2 or 3 button key, sometimes the 3rd button is not fitted and sometimes the case does not have the indentation for the tactile button.

In the bottom of the ignition switch you have the IR pick up seen in the second picture
 

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wardpaa

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Thanks Malc.
Pressing any of the buttons with the key inserted does not make any difference on the chrome key and I have swapped the coils. The coil in the chrome key is slightly shorter, but the PCB has unused tracks ready for the larger size coil found in the old style fobs, so swapping is easy. Both also have a similar resistance 0.6 ohms (old) 0.4 ohms (new).
Do you have a close up photo of a new style chrome PCB (button side and Chip side) ?

Surely if the key is not activating EIS when keys are pressed, when batteries and IR are used, therefore the keys output is the wrong code and must be seperate than that of the code used to unlock the car ?
 
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television

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I do not have pictures now of the chrome key :( the coil was modified to stop them from falling off and are both electronically the same.

I do know that the chips are made so that the pin outs for the functions are as near as possible to those parts of the key that it drives so any fault when the chip was transferred would be in the leading edge towards the front.

I have been thinking of setting up a test bed for the testing of the transponder sections, using an old ignition switch but have not got around to it yet.
 
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wardpaa

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Malc, Do you know for certain whether a pre used Chrome key does work when the Chip is transfered ? This is the acid question i wanted to prove on the original thread. People have claimed to have made it work, but when you probe for additional answers such as 'does it start the car then' ?.. it kind of goes all quiet.
There could be various combinations of Chrome keys vs car models and years that we do not know about, OR the mod also may involve the 2nd chip which is not transferable.

Thanks for your input on this.
 

C320andy

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just to bump abit here....If I were to buy a chrome key from ebay and swap all of the internals over, theroryetically should it all work the same but in a new shiney chrome remote fob?
 

television

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just to bump abit here....If I were to buy a chrome key from ebay and swap all of the internals over, theroryetically should it all work the same but in a new shiney chrome remote fob?

The PCB from a plastic key will not fit inside the chrome key case.
 

television

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Further thoughts Wardpaa the through hole plating can fail anywhere on these keys,, on many a key I have had to pop a thin wire in and solder both sides
 
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wardpaa

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I am going to buzz the tracks through later from the coil. Have done the chip but want to check the through holes around the chip area where heat may of caused an OC. Visibly all looks OK and I have probably spent hours on this thinking that I should put the chip back and call it quits, but will do this first.
 

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