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My Golf 7 key was stolen.

I have reprogrammed my keys to disable the stolen one.

The thief could still reprogram the stolen key as he can open the door using the hidden emergency door lock.

Which fuse can I remove to disable car key reprogramming and/or engine start so the thief can’t take over the car?

I am aware some thiefs might know which fuse is missing, but this is as far as I am going to go for now in tampering with the car.

I don’t own OBD gear so I can’t test if “F18 5A Battery control module, data bus onboard diagnostic interface” is the right one. Also I don’t know the long term consequences of removing any of the fuses.

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  • Welcome to Motor Vehicle Maintenance & Repair! In most vehicles, when you reprogram keys, it reprograms ALL keys. You have to have keys presents at the time of reprogramming in order for them to work. If the other key wasn't there, it wasn't reprogrammed into the computer and therefore won't work. I don't know if this holds true for your Golf. Commented Feb 25, 2023 at 13:35
  • There is no fuse to remove to disable immobilizer programming.
    – narkeleptk
    Commented Feb 25, 2023 at 13:49
  • @Pᴀᴜʟsᴛᴇʀ2 Yeah, but since the thief has the physical imprint he can open the door (for my car) even if the key is disabled for remote unlock and ignition. He can then proceed to access the OBD port to reprogram his key authorization and thus also disable my keys which obviously aren’t present during the reprohgramming. In effect he is taking control of the car and can simply drive off.
    – oxygen
    Commented Feb 25, 2023 at 17:52
  • @narkeleptk Well it needs power and there is a fuse for everything so I doubt there is no fuse.
    – oxygen
    Commented Feb 25, 2023 at 17:55
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    @oxygen - I thought about the "access" to your car after I wrote that and agree. There is no way programmatically to eliminate this threat. The only way to do that is to replace the outside physical lock with a new one and a new cut. You say "... and can simply drive off." ... there's nothing simple about what you're saying. They may be able to get access into your car, but they won't simply be able to drive off. It takes equipment and knowhow. Commented Feb 25, 2023 at 18:03

1 Answer 1

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There is no fuse to remove that will disable immobilizer programming. You can how ever remove the fuse for the obd2 power. That will slow someone down since their tool would no longer be powered and they probably will not be prepared with the additional attachments to deal with that. You could also just install a dummy obd2 port and hide the real one behind the paneling.

Also, unless you know the cars immobilizer pin code VW's of this year are very difficult to program. Without knowing the PIN, immobilizer data and the key no longer being programmed, The thief would need to do a ALL KEYS LOST procedure to reprogram it. Its the same thing that would need to be done if it was a never programmed before key. Typically these can not be done through OBD2 alone and requires removal and disassembly of the instrument cluster.

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  • “The thief would need to do a ALL KEYS LOST procedure to reprogram it” Car key reprogramming guys offered this service too. I’m not too savvy but I would guess they don’t need VW’s secret PIN or smth like that (at least for my car?).
    – oxygen
    Commented Feb 25, 2023 at 17:53
  • Can you confirm F18 disables the OBD power?
    – oxygen
    Commented Feb 25, 2023 at 19:18
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    @oxygen I am a locksmith. We do indeed need the PIN & a precoded key to program AKL through OBD2 on your VW. That is why I mentioned in the second part its not possible to do solely through OBD2 without that info. These years we need to force the immobilizer system into service mode so that we can extract the needed immobilizer data. This is done by removing the instrument cluster where the immobilizer is located and hacking the memory to think its in service mode which allows our tools to access the needed information. Anyone who could program AKL,doesn't need help from a old unprogrammed key
    – narkeleptk
    Commented Feb 25, 2023 at 19:41
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    Thanks man, that’s really reassuring.
    – oxygen
    Commented Feb 25, 2023 at 21:22
  • Hey locksmith... couldn't OP change the locks so the original key cut doesn't work anymore? Is that a locksmith job or do they need to go to VW? Commented Feb 26, 2023 at 1:11

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