Club 80-90 Forums

Does anyone know a way to find the 4 digit pin that VCDS requires to be able to do things like add new keys?
I've been reading a lot of forums but I'm going round in circles.
It is a golf MK 3 AHU engine, ECU, immobiliser and keys but I need to add a spare key and the nerd in me would like to be able to do it myself.

There are bits of software floating about the internet and available commercially which claim to be able to recover device PIN's from immo units and so on. I've used one to work with the Golf Mk4 and similar dash panels. I've not found one to work with those immo units though. Several of the old forums I used to use, including a couple of german ones, have closed down unfortunately so a lot of the knowledge of the older systems is becoming harder to find. Good luck ! You could just get the key cloned at Timpsons..
 

You need to extract the EEPROM data from the ECU or the immobiliser box, then look at the specific memory location where the code is stored.

Sometimes you need to physically desolder the EEPROM chip to read it, but on later stuff (mk4 golf onwards) you can do it through OBD.

https://www.youtube.com/watch?v=eJnCWNKf0gk

Also bear in mind that some aftermarket replacement keys may come with a universal "T5" chip in them which has no ID until it's programmed with a locksmith tool, so ideally you'd use a 2nd hand OE vw transponder.

Bearing in mind (iirc, I'm a bit rusty..):

G3 = Immo2, fixed code, ceramic chip, immo PIN not in ECU
G4 (99-on) = Immo3, rolling code, glass ID48 chip, ECU knows PIN

They are different things, similar approaches may work, but the devil is in the detail. The vid linked shows the software that works on some things including the G4 clusters, it does not in my experience work with the G3 immo boxes.

By the way I've a dozen or more of the immo boxes here which are e-waste to me, if anyone thinks they can extract the Immo PIN's and make some use of them, they can have them for the postage cost.

Yes, I bought a brand new immo box in a panic when I had immobiliser issues recently (it was just a blown fuse which I found thanks to this forum), thought I could plug it in and start the van, but no, the Ecu presumably, needs to be told that it has a new immo box. I thought it was just a communication device between the key reader and the ECU.
As you can see, I am a bit confused about what is where and what VCDS is talking to at any point.
Are you saying that the pin is to access the immobiliser unit (separate little brown box for clarity) and everything is matched to that?
From VCDS website info, it looks like my 97 Golf 3 has immo1 (as it contains 3Z in the serial number)