VW key/remote, and immobilizer information and troubleshooting
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General introduction
The immobilizer is an anti-theft device located in the instrument cluster using a chip in your key with an antenna or "pick up" at the ignition cylinder.  Later generations also are more tied into the ECU.  You cannot do an immobilizer bypass with normal "car theft" tools so don't bother asking.  If your TDI is 1999 or earlier, it does not have an immobilizer.  When buying or programming a new key, you must use a key that corresponds to the same immobilizer generation and keyless entry type and sync it to the immobilizer.  If you are interested in getting a new key, read the summary below and refer to either 1000q: mk4 key programming or 1000q: mk5 key/remote FAQ 

The main symptom of a faulty immobilizer system is the car shutting off after two seconds or the anti-theft light on the dashboard flashing, later generations may also have a beeping noise with the immo light flashing.  A very low car battery or car battery removal could also trigger the immobilizer.  Some people report certain computers with wireless internet activated in the car interfering with the transmitter in the key of the immobilizer.  If you want to be super careful, don't let the key get exposed to high strength microwaves.  Standing next to a microwave won't do anything but putting the key into a microwave will quickly damage the chip (and possibly the microwave).  

The first step in getting a new remote/key

The remote/key is actually 3 different parts.  The keyless entry remote, the flip key, and the immobilizer.  Each must be correct to the car for the remote to work as intended.    You must program the immobilizer in addition to the keyless entry or else the immobilizer will shut off the engine after 2 seconds. The immobilizer has nothing to do with unlocking the doors, the alarm, or the starter, it still lets the engine start briefly. 

• If you have no immobilizer you can program the keyless entry yourself and have a new key cut almost anywhere
• If you have an immobilizer and have an existing broken key (broken remote or flip key), remove the immobilizer chip from the old key and swap it into your new key or else the engine won't stay running.  In other words, remove the new chip in your new key and replace it with your old chip from your old key.  The chip looks like a small grain of rice.  This is pictured below.  Then you can program the keyless entry yourself and have a new key cut almost anywhere.  You could tape it to the outside of the ignition cylinder but that defeats the point of the immobilizer anti-theft.
• If you have an immobilizer and you don't have an old key to salvage the chip out of, you must read the notes below about the SKC code and key variations.

Keys and immobilizer differences by year
If you have the yellow car symbol pictured a few paragraphs below on the instrument cluster, you have an immobilizer.  The three main types of VW TDI immobilizers are immo-2,  immo-3, and immo-4.  VW up to 1999 do not have an immobilizer and immo-1 was not equipped on cars sold in the US.

• no immo - you can swap keys, ECUs, and instrument clusters without any further programming
• Immo2 - found on mk4 cars, you need SKC to use a new key or instrument cluster, it has an emergency drive function that will let you drive to the dealership or mechanic for them to fix but you must know the SKC code.
• Immo3 - found on mk4 cars, you need SKC to use a new key, instrument cluster, or ECU.
• Immo4 - found on mk5 cars, you need SKC to use a new key, instrument cluster, or ECU.

2000-2001 were transition years for immo2 in the US.  If your VW is model year 2002-2005, it probably has immo-3.  Immo-4 is on 2005.5-2006 and newer mk5 cars. 

Because of the variation in build dates, immobilizer generations, and remote compatibility, I recommend going to the dealer for replacement keys if you don't have an old key to salvage the immobilizer chip out of.  It is expensive, but they can setup the immobilizer and if it's the wrong part they'll take it back.  If you buy an ebay replacement key for an immobilizer car you have to figure out how to program the immobilizer, if your car was a transition year, and there are no refunds once you cut a key.  The part numbers below are only a guide, double check the correct part number with your parts vendor, this website is not responsible if you order the wrong key!  

• If you have a car with build date 11/98-09/00, (about model year 1998-2001) your remote probably looks like #1 pictured below, part number should be VW# 1j0 959 753 f
• If you have a car with build date 10/00- 05/01 (about model year 2000-2002), you probably have the remote that looks like #1, it should be VW# 1j0 959 753t.  
• If you have a car built after 05/01 (about model year 2001-2002), you should have remote #2, it is either VW# 1j0 959 753 am or 1j0 959 753 dc
• If you have an mk5 body car you have immo4, your Jetta remote is either VW# 1j0 959 753p, or 1k0 959 753h.

Secret Key Code (SKC) info - you MUST have a SKC to work on the immobilizer!

The SKC is needed to program new keys or clusters.  It's a 4 or 7 digit code that you use with vag-com.  *If your program asks for a 5 digit SKC code, simply input a "0" as the first digit.  From 2000-2001, VW gave a black plastic tag that had the SKC printed on it.  If you cannot find this then you cannot input the SKC!  VW no longer has access to give you any SKCs.   After 2001, VW used a 7-digit SKC which was really an encoded 4 digit SKC.  The dealer input it into their diagnostic tool which translated it into a 4 digit SKC.  After 2005, VW used something called the Geko system for distributing SKCs.  The SKC goes directly from the Geko Server to the diagnostic tool.  The VW tech never sees any code so they cannot give any codes to you!

If you want your SKC you must find the black plastic key code, contact someone who has tools to retrieve the SKC from the instrument cluster, or buy a tool to retrieve the SKC.  Vag-com software or the dealer cannot retrieve the SKC.  If you happen to have an old -7-digit encoded SKC, you can use it with your vag-com and vag-com will translate it into a 4 digit code.

Because of this trouble with SKCs, the dealer is a good option for getting new keys.  They will cut the key and program it.  In addition, they will also guarantee that the immo generation is compatible with your car.  While it is expensive, it may be cheaper than buying the software to get the SKC and keys and doing it yourself.  If you still want to get the 4-digit SKC, search for "Vag-Tacho" software.  You can buy a copycat version of it off ebay that may work.  If you have a CAN BUS car, Vag-Tacho will not work, you need VAG Commander.  Some mk4 cars may still use dual line K depending on the market (Europe, Asia, etc).  Also, vag-com cannot get an SKC for you and they do not plan on incorporating this hacking feature.

Problems that are NOT related to the immobilizer system

• If the starter does not engage or the engine does not "turn over" at all, this is not an immobilizer problem.  
• The chip inside the key does not have a battery or other internal electricity source because it is an RFID chip and is "excited" by the transmitter.  Shaking the key or changing the remote key's battery will not fix any problem with the immobilizer.  
• It also has nothing to do with opening or unlocking the doors.  The immobilizer will not be activated by the alarm system, it only has to do with starting the car.  
• It also has nothing to do with the power of the car.  If your car has poor performance or fuel economy, it has nothing to do with the immobilizer.  See 1000q: limp mode for the TDI for more details.

This article is separated into immo-2 and immo-3 sections because they have different procedures.  Immo-4 general overview is also included, troubleshooting procedures are similar to earlier cars.  Note that to work with the immobilizer, you MUST have a vag-com.  You cannot use a generic code scanner, you must use a vag-com cable.  You can only use an emergency start without a vag-com. and even then you must know the SKC code.

Also note that immo-2 and immo-3 keys are not compatible.  If you have an immo-2 car, you must use an immo-2 remote/key.

General troubleshooting procedures

1.  First, make sure the car battery is charged.  A low battery can cause problems with the immobilizer.

2.  Try another key - you should have a valet key and spare key that also have an immobilizer chip in them.  If they work, then you have isolated the problem to the key.  Again, there is NO battery for the immo chip, it gets power from the ignition switch transmitter.  You can try reprogramming the chip with the procedures linked to below.

3.  Check for error codes - scan the car with a vag-com to see if there is a problem with the system and refer to the appropriate procedure below.

4.  You can try just leaving the key in the ignition to "ON" but not start for a few minutes. Many people report that the light just goes away after 10 minutes as if nothing ever happened.

5.  Try disconnecting BOTH negative and positive terminals of the battery.  Then touch the cables to each other only, while not attached to the battery.  This can reset the immo system.  Again, don't touch the cables to the battery, only to each other while both are disconnected from the battery - you don't want to short the battery out.

6.  Check wiring and plugs at instrument cluster and pickup coil at the ignition switch, there is a chance it could be faulty.

Model specific detailed information and procedures

Immo-1 - was never equipped on a car in the US

Immo-2 information and troubleshooting (2000-some 2002)

Immo-3 information and troubleshooting (some 2002-2005)

Immo-4 information and troubleshooting (2005.5-2006)

Image of key disassembled - note that the immobilizer chip (yellow arrow) needs no battery - it is energized by the pick up antenna on the ignition coil.  

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