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Discussion Starter #1 (Edited)
I am prompted to write this short guide due to the general misinformation and unjustified 'fear' people seem to have with regard to the Siemens/VDO immobiliser and it's use in the T4 1.9TDI conversion. In short, if it worked in the donor car then there is absolutely no reason why it should not work in your van.

Before I give a detailed description of the Siemens/VDO type immobiliser (commonly known as Immobiliser 2) as fitted to most late 94->2000 VAG cars, here's a quick overview:

Passive Immobilisation

The introduction of passive vehicle immobilisation by the major car manufacturers came about because the brokers for the Insurance Federation of Germany began to refuse to underwrite vehicles that did not have passive electronic immobilisation systems fitted. The use of the word 'passive' meant that no direct intervention was required by the user to 'activate' or 'deactivate' the system. Some of you may remember Peugeot marketing an immobiliser in their vehicles in the 1990's which required the user to input a PIN on a keypad before starting the vehicle - this is an example of an 'active' system as it requires user intervention.


So how does VW Immobiliser 2 work?

The passive Siemens/VDO transponder system fitted to most VAG group cars at least between late 1994 and 2000 comprises of three primary components: 1) The immobiliser control unit, 2) The key (a transponder or RFIC device - you may hear people call it a 'chip') embedded within the body of the key or fob, and 3) The key reader antenna attached to the ignition barrel. The immobiliser 2 control unit interacts with the ECU and instrument cluster, (and body electronic systems on some vehicles). It is important to note that the key is paired (or matched) to the immobiliser not the ECU.

The Siemens/VDO immobiliser control unit:


The transponder RFIC (found inside the key):


The key transponder reader antenna array:


When an attempt is made to start the vehicle, the control unit transmits a burst of RF (Radio Frequency) energy at a given frequency - to the key reader antenna around the ignition barrel. The RFIC or 'chip' in the key contains a tuned circuit which is matched to the frequency of this burst of RF, as a result a small voltage is then generated by induction within the transponder device. This small amount of induced RF energy is used to charge a capacitor, which is used to power the RFIC device. The RFIC then responds by transmitting (again by RF), a unique individual thirty two (32) digit identifier (number). This all happens seamlessly and in microseconds, so the user never notices
If the immobiliser 2 unit 'recognises' the identifier transmitted by the RFIC as a 'known' vehicle key, it then sends a message to the ECU to allow it to be 'unlocked' and hence allow the vehicle to start. A common sign of a faulty immobiliser system is that the vehicle will start but will only run for 1 or-so seconds.
The two main manufacturers in immobiliser transponder (RFIC) technology are Philips (see pic above), and Texas Instruments - both of which are used on VAG vehicles. Although it is Philips devices which are used in most of the immobiliser 2 systems.


So what do I need to know when wiring the immobiliser for the 1.9 TDI conversion?

From the donor car, you will need:

1) Siemens/VDO immobiliser control unit (as pictured above),
2) Original key (or RFIC device from the key as shown in pic above - not strictly required, but makes life easier - see FAQ )
3) Key transponder reader
4) The ECU.


There are two connectors on the control unit:



One is a 3 pin connector the other is 6 pin.

* The 3 pin goes to the transponder key reader antenna array.
* The 6 pin connector is numbered (as you can see) pins 1 to 6


So starting at the start:

Pin 1 - Black , connect this to an ignition switched +12v supply

Pin 2 - Grey/white, goes to the ECU (pin 61 for Bosch 68-pin ECUs)

Pin 3 - Grey goes to the OBD II diagnostic socket, but changes to a grey and white at the diagnostic socket end.

Pin 4 - Brown, ground

Pin 5 - Not connected

Pin 6 - Brown, ground


Pin 1 was originally connected to the donor vehicle instrument cluster and got it's +12v supply from there.
If you removed the cluster( therefore no +12v to pin 1) the immobiliser will not function - engine will start and run for a second and then stop.




Alternatively, if your donor vehicle came with the above immobiliser (usually made by TEMIC or Sagem, but Siemens/VDO also made them), then usually they will have an 8-pin connector for the power and diagnostic functions rather the the six pin connector outlined above it is connected as followed:

Pin 1 = B+ (12V)

Pin 2 = +12_IGN

Pin 3 = N/C

Pin 4 = GND

Pin 5 = GND

Pin 6 = N/C

Pin 7 = Engine k-line

Pin 8 = k-line diagnostic socket




FAQ

1. Is there any way I can bypass the immobiliser

Simple answer: 'No' otherwise this would defeat the purpose of the manufacturer fitting an immobiliser to begin with.

More complex answer: 'Yes' - you can have the firmware of the ECU modified such that it does not expect to receive a message from the key via the immo box thus doing away with the immobox reader coil and key altogether. This can be expensive however ~£85GB at the time of writing (11/2010).

Another "solution" is to fit a immobiliser emulator, which are available from a 3rd party companies, cost at the time of writing is about £55. However it may just cheaper and easier to buy a key/immo box pair from a local scrapyard

Personally, I do not understand why anyone would want to remove the immobiliser. It will after all make your van harder to steal which for me at least is a always a bonus.


2. I bought an engine/harness/immobiliser but I didn't get any key/key was lost/incorrect etc.. Is there any way I can get a new key(s) programmed?


Yes, some locksmiths/dealers/independents will do this but only if you have the SKC (Secret Key Code - comes on a tag with the car when it was new - most have long since been lost). Others locksmiths/dealers/independents can do it without the SKC, but they charge accordingly ~£50-80.

If you have the SKC and a fully registered copy of VAG COM/VCDS you can do it yourself.

Alternatively, for a small fee (strictly to cover costs), If you send me the immobiliser I can extract the SKC from your immo box so that new keys can be coded to your immobiliser, or if you send me a new key I can adapt that to the immo. (PM me for details)



Troubleshooting

You will not be able to do any diagnosis without a copy of VAGCOM to interrogate the immobiliser

The immo system (apart from a power supply) essentially depends on two things: 1) A good signal from the key and 2) A reliable link to the ECU The only way to test the integrity of these is with VAGCOM

When installing the antenna (which is often incorrectly described as a coil because of its shape), you should never put the key 'in-the-middle' of the antenna to test the immo, this will only result in a poor/no signal to the immo box. The best way to ensure a reliable signal is to fit the key reader to the ignition barrel in the van and the correct transponder to the key. The reason for this is that the RF signal that the transponder generates is so small that positioning is critical. In addition to this, the ignition barrel acts as a ground-plane for the antenna array to improve the propagation of the transponder signal. VAGCOM will report 'intermittent of poor signal from key' type faults if you problems in this respect.

If you have problems with the datalink k-line to the ECU, then either the immo will report a comms failure or the ECU will give you a 'Engine start blocked by Immobiliser'.



Hope this helps with understanding and wiring of the immobiliser system and clears up any mystery that surrounds the 'magic' of VW immobiliser 2.
 

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excellent guide mate much appreciated T:;)
will undoubtedly assist people in their conversions as i know it has/will me. so thank you for your time in writing it.

sticky for sure??????

cheers jaz
 

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yep just found the chip in the key,,and just took out my old one out of my key put the golf chip in jobs a good one saves me changeing my barrel now.and runs fine A:
 

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I am prompted to write this short guide due to the general misinformation and unjustified 'fear' people seem to have with regard to the Siemens/VDO immobiliser and it's use in the T4 1.9TDI conversion. In short, if it worked in the donor car then there is absolutely no reason why it should not work in your van.

Before I give a detailed description of the Siemens/VDO type immobiliser (commonly known as Immobiliser 2) as fitted to most late 94->2000 VAG cars, here's a quick overview:

Passive Immobilisation

The introduction of passive vehicle immobilisation by the major car manufacturers came about because the brokers for the Insurance Federation of Germany began to refuse to underwrite vehicles that did not have passive electronic immobilisation systems fitted. The use of the word 'passive' meant that no direct intervention was required by the user to 'activate' or 'deactivate' the system. Some of you may remember Peugeot marketing an immobiliser in their vehicles in the 1990's which required the user to input a PIN on a keypad before starting the vehicle - this is an example of an 'active' system as it requires user intervention.


So how does VW Immobiliser 2 work?

The passive Siemens/VDO transponder system fitted to most VAG group cars at least between late 1994 and 2000 comprises of three primary components: 1) The immobiliser control unit, 2) The key (a transponder or RFIC device - you may hear people call it a 'chip') embedded within the body of the key or fob, and 3) The key reader coil attached to the ignition barrel. The immobiliser 2 control unit interacts with the ECU and instrument cluster, (and body electronic systems on some vehicles). It is important to note that the key is paired (or matched) to the immobiliser not the ECU.

The Siemens/VDO immobiliser control unit:


The transponder RFIC (found inside the key):


The key transponder reader coil:


When an attempt is made to start the vehicle, the control unit transmits a burst of RF (Radio Frequency) energy at a given frequency - to the key reader coil around the ignition barrel. The RFIC or 'chip' in the key contains a tuned circuit which is matched to the frequency of this burst of RF, as a result a small voltage is then generated by induction within the transponder device. This small amount of induced RF energy is used to charge a capacitor, which is used to power the RFIC device. The RFIC then responds by transmitting (again by RF), a unique individual thirty two (32) digit identifier (number). This all happens seamlessly and in microseconds, so the user never notices
If the immobiliser 2 unit 'recognises' the code number transmitted by the RFIC as a 'known' vehicle key, it then sends a message to the ECU to allow it to be 'unlocked' and hence allow the vehicle to start. A common sign of a faulty immobiliser system is that the vehicle will start but will only run for 1 or-so seconds.
The two main manufacturers in immobiliser transponder (RFIC) technology are Philips (see pic above), and Texas Instruments - both of which are used on VAG vehicles. Although it is Philips devices which are used in most of the immobiliser 2 systems.


So what do I need to know when wiring the immobiliser for the 1.9 TDI conversion?

From the donor car, you will need:

1) Siemens/VDO immobiliser control unit (as pictured above),
2) Original key (or RFIC device from the key as shown in pic above - not strictly required, but makes life easier - see FAQ )
3) Key transponder reader coil
4) The ECU.


There are two connectors on the control unit:



One is a 3 pin connector the other is 6 pin.

* The 3 pin goes to the transponder reader coil.
* The 6 pin connector is numbered (as you can see) pins 1 to 6


So starting at the start:

Pin 1 - Black , connect this to an ignition switched +12v supply

Pin 2 - Grey/white, goes to the ECU (pin 61 for Bosch 68-pin ECUs)

Pin 3 - Grey goes to the OBD II diagnostic socket, but changes to a grey and white at the diagnostic socket end.

Pin 4 - Brown, ground

Pin 5 - Not connected

Pin 6 - Brown, ground


Pin 1 was originally connected to the donor vehicle instrument cluster and got it's +12v supply from there.
If you removed the cluster( therefore no +12v to pin 1) the immobiliser will not function - engine will start and run for a second and then stop.


FAQ

1. Is there any way I can bypass the immobiliser

Simple answer: 'No' otherwise this would defeat the purpose of the manufacturer fitting an immobiliser to begin with.

More complex answer: 'Yes' - you can have the firmware of the ECU modified such that it does not expect to receive a message from the key via the immo box thus doing away with the immobox reader coil and key altogether. This can be expensive however ~£85GB at the time of writing (11/2010).


2. I bought an engine/harness/immobiliser but I didn't get any key/key was lost/incorrect etc.. Is there any way I can get a new key(s) programmed?


Yes, some locksmiths/dealers/independents will do this but only if you have the SKC (Secret Key Code - comes on a tag with the car when it was new - most have long since been lost). Others locksmiths/dealers/independents can do it without the SKC, but they charge accordingly ~£50-80.

If you have the SKC and a fully registered copy of VAG COM/VCDS you can do it yourself.

Alternatively, for a small fee (strictly to cover costs), If you send me the immobiliser I can extract the SKC from your immo box so that new keys can be coded to your immobiliser, or if you send me a new key I can adapt that to the immo. (PM me for details)



Hope this helps with understanding and wiring of the immobiliser system and clears up any mystery that surrounds the 'magic' of VW immobiliser 2.
are i have a 8 pin plug on the immobiliser not a 6pin engine ahu came from a caddy 2000 1.9 tdi need the immo wiring HELP
 

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Hi there I've just got my golf tdi 1994 m 1z for a donor vehicle for me t4 its not got a immobiliser on it but me t4 has is this Going to be a problem?:confused:
 

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Hi guys new to t4s I have a v 2,000 reg 1.9 td with an immobilliser I'm converting the vehicles to 1 z tdi from a golf m1994 with out an immobilliser is this going to be a problem????
 

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Hi guys new to t4s I have a v 2,000 reg 1.9 td with an immobilliser I'm converting the vehicles to 1 z tdi from a golf m1994 with out an immobilliser is this going to be a problem????
 

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Good post, on the SIEMENS 8 pin connector is pin 1 a permanent 12v feed, as my car will not start and pin 1 has no voltage but pin 2 has 12v supply when ignition is turned on .
Thanks
 

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My antenna from the donor car (golf) is alot bigger than my vans one. Can i just plug in my vans antenna to the golf immo box? Or will that not pick up the golfs keys chip?
 
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