Hello,
I thought I'd write a quick post to describe how to extract the SKC (Pin code) from a separate immo 2 box found on some T4s made earlier than 2001. You need this is if you want to program new keys using vcds. If you are lucky then your immo and key locations are held in the cluster, and then you can use vag-tacho or others to read the eeprom through the OBD2 port.
If you have a separate immo 2 box then the part number will likely be 6H0953257A/B and is easily accessed by removing the steering cowling, then the instrument housing cowling and it is on the left hand side. Once removed, you need to open it up and locate the 28 pin TMS chip - which is here:
![Image]()
Unfortunately you cannot read the EEPROM without desoldering the chip. If you can't desolder the chip you might find a friendly TV repair place will be able to, and you can either socket it, or just read it using a generic TMS programmer and replace. The eeprom looks like this:
![Image]()
the pin is mentioned 4 times in hex at positions (91,92), (93,94), (191,192),(193,194). In my case this was 2261 in hex - this translates as 8801 in decimal.
In order to then program keys you need to follow the immo 2 vcds key programming procedure here using the pin code you found in decimal with a "0" in front - so mine was 08801.
I got a replacement immo box first so I could tinker with it and make sure I still had a working box. If you do that you need to "introduce" the immo to the ECU as described here (using channel 25). Then go ahead to the key programming part.
The transponder chip you need for this sort of key is ID42, and the blade is an HU49 - both are cheaply available, and you don't need to sell a kidney to get the dealer to program a new key for you.
As a result of this tinkering I now have a spare immo box for which I know the SKC - if that's of interest to someone let me know.
Thanks a lot to LawAnderson for his encyclopaedic knowledge about these things - after chats with him I figured this out, but it took a while for me to understand. In essence the TMS chip holds the key and the transponder information about the keys. In newer models this is all held in the cluster and readable with vag-tacho (for example).
I thought I'd write a quick post to describe how to extract the SKC (Pin code) from a separate immo 2 box found on some T4s made earlier than 2001. You need this is if you want to program new keys using vcds. If you are lucky then your immo and key locations are held in the cluster, and then you can use vag-tacho or others to read the eeprom through the OBD2 port.
If you have a separate immo 2 box then the part number will likely be 6H0953257A/B and is easily accessed by removing the steering cowling, then the instrument housing cowling and it is on the left hand side. Once removed, you need to open it up and locate the 28 pin TMS chip - which is here:
Unfortunately you cannot read the EEPROM without desoldering the chip. If you can't desolder the chip you might find a friendly TV repair place will be able to, and you can either socket it, or just read it using a generic TMS programmer and replace. The eeprom looks like this:
the pin is mentioned 4 times in hex at positions (91,92), (93,94), (191,192),(193,194). In my case this was 2261 in hex - this translates as 8801 in decimal.
In order to then program keys you need to follow the immo 2 vcds key programming procedure here using the pin code you found in decimal with a "0" in front - so mine was 08801.
I got a replacement immo box first so I could tinker with it and make sure I still had a working box. If you do that you need to "introduce" the immo to the ECU as described here (using channel 25). Then go ahead to the key programming part.
The transponder chip you need for this sort of key is ID42, and the blade is an HU49 - both are cheaply available, and you don't need to sell a kidney to get the dealer to program a new key for you.
As a result of this tinkering I now have a spare immo box for which I know the SKC - if that's of interest to someone let me know.
Thanks a lot to LawAnderson for his encyclopaedic knowledge about these things - after chats with him I figured this out, but it took a while for me to understand. In essence the TMS chip holds the key and the transponder information about the keys. In newer models this is all held in the cluster and readable with vag-tacho (for example).
