Hi everyone,

Before posting, I want to clarify that I have already searched MBWorld extensively regarding W221 KEYLESS-GO replacement issues and reviewed multiple discussions, but have not found a clear answer specific to my situation and my vehicle. Therefore, I am hoping to get input from members familiar with late-model W221 FBS3 systems.

Vehicle:

2013 Mercedes-Benz S350 BlueTEC (W221)

Factory option 889 – KEYLESS-GO

VIN available if needed

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Original key (lost):

• FCC ID: IYZDC10

• Full passive entry operational

• Door handle unlock worked

• Push-button start worked without key insertion

(Photos of the original key are attached for reference.)

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Replacement key supplied by the dealership:

• Part number: 204-905-11-04-9999

• FCC ID: IYZDC11

• Remote lock/unlock functions correctly

• Passive KEYLESS-GO does NOT function

• The vehicle now requires key insertion to start

The dealership provided the following written explanation:

“Unfortunately, Mercedes-Benz no longer supports that feature; the keys for the Keyless Go option are no longer available. As of right now, the keys for the Keyless GO option are no longer available.”

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I am trying to determine whether this is:

• A true parts supersession issue

• A hardware revision difference between IYZDC10 and IYZDC11

• A low-frequency (LF) antenna limitation in the replacement key

• Or a coding/configuration issue within the EIS/FBS3 system

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I hope you will appreciate the fact that I have already paid a considerable amount for the dealership-supplied key, and it does not restore the full KEYLESS-GO functionality my vehicle originally had. I am understandably trying to avoid repeating that expense without fully understanding the technical cause. I am looking for a reliable and independent Mercedes-Benz locksmith who can provide a replacement key fob that restores complete factory functionality and am seeking someone knowledgeable who can provide that at a fair and reasonable cost.

Technical Questions:

1. Is there a confirmed hardware difference between FCC ID IYZDC10 and IYZDC11 affecting passive entry functionality?
   
2. Has anyone with a late W221 successfully restored full factory KEYLESS-GO after losing the original key?
   
3. Are there reputable independent specialists capable of supplying/programming a genuine KEYLESS-GO capable key without replacing control modules?
   
4. Could this realistically be a coding issue rather than hardware?
   

I am located in Central California but willing to travel if necessary for the replacement KEYLESS-GO fob.

I appreciate any technical insight from members experienced with W221 KEYLESS-GO and FBS3 systems.

Thank you.


Photos of the original key, which I lost, are attached for reference: