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VW and Audi key/remote, and immobilizer theft deterrent system information and troubleshooting

General introduction
The immobilizer is a theft deterrent system located in the instrument cluster, a radio frequency identification (RFID) chip in the key, and an antenna at the ignition cylinder.  You cannot do an immobilizer bypass with normal "car theft" tools so don't bother asking.  If your TDI is 1999 or earlier and sold in North America, it shouldn't have an immobilizer.  If your car has the yellow car/key symbol on the instrument cluster (shown activated below) it has 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 need a new key, read the summary below and refer to the detailed instructions at 1000q: mk4 key programming or 1000q: mk5 key/remote FAQ .  If you have an Audi A3, the steps in VW mk5 mostly apply.  If you have a mk3 VW you don't have an immobilizer but here's 1000q: mk3 key programming FAQ anyways.  Audi followed different generations but the same basic procedures apply.

The main symptom of a faulty immobilizer system is the car shutting off after a second or the yellow car/key on the dashboard flashing.  A very low car battery or car battery removal could also trigger the immobilizer.  Very rarely, it's triggered for unknown reasons, see below for troubleshooting.  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 damage the chip (and maybe the microwave).

The immobilizer chip has a range of about 1" through plastic and about 3" when out of the key.  Although the computer constantly monitors if the chip is correct or not, it won't shut off the engine after the first few seconds of the car engine starting.  I'm pretty sure that it won't shut off the engine if the chip signal is interrupted after a few minutes. (I don't want to test it by driving around without the chip signal).  Once nice thing about the immobilizer system is that if a key is stolen/lost, having the keys reset by the dealer or someone with the correct key matching tools will prevent the lost key from operating the car as normal.  After the keys are reset, an old metal key/remote half can still open the doors but won't let the engine run for more than 1 second.

The first step in getting a new remote/key

The remote/key is 3 different parts: the keyless entry remote, the metal flip key, and the immobilizer chip.  Each must be correct for the remote to work as intended.  For example, even if you buy a cut key, the unprogrammed immobilizer chip will shut the engine off after a second.  The immobilizer has nothing to do with unlocking the doors, the alarm, or the starter - it still lets you start the engine but if it's not programmed it will shut the engine off.

-If the car has an immobilizer and you 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.  The chip looks like a small grain of rice, pictured below.  Then you can program the keyless entry yourself.  If you need a new metal key, just take the key apart and swap the metal key with a new one.  You can cut the new metal key anywhere which does side mill/reverse cut/laser cut VW/Audi sidewinder keys.

-If the car has 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.

The key disassembled - again, the immobilizer chip (white arrow) uses no battery - it's an RFID chip energized by the pick up antenna on the ignition coil.

Keys and immobilizer differences by year
If you have the yellow car symbol pictured below on the instrument cluster, you have an immobilizer.  The three main types of VW TDI immobilizers are immo2,  immo3, and immo4.  VW up to 1999 do not have an immobilizer because immo1 was not equipped on cars sold in North America.  Immo2, 3, 4, and 5 keys are not compatible.  In other words, if you have an immo2 car, you can only use an immo2 key.  2000-2001 were transition years for immo2 in the US.  If your VW is model year 2002-2005, it probably has immo3.  Immo4 is on 2005.5-2006 and newer mk5 cars.  Immo5 is found on the newest Audi.

-Immo2 - found on mk4 cars, you need SKC to use a new key or instrument cluster, but you can still swap ECUs.  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.  You can buy a used key and it will work if you reprogram the immobilizer chip using the SKC.

-Immo3 - found on mk4 cars, you need SKC to use a new key, instrument cluster, or ECU.  You cannot use used keys from another car since the immobilizer chip can only be set once per car.

-Immo4 - found on mk5 and mk6 cars, you need SKC to use a new key, instrument cluster, or ECU.  You cannot use used keys from another car since the immobilizer chip can only be set once per car.

-Immo5 - found on 8T generation Audi A4 (2007/2008+) and 8k generation Audi A5 (2007+).

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's expensive, but they can match the key to the car 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 absolute cheapest way to get a new key is to buy a cut key online and take it to the dealer for programming.  Regardless of the number of keys, they will charge you 1 hour minimum even though it takes about 5 minutes.  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 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 VW you have immo4, your Jetta remote is either VW# 1j0 959 753p, or 1k0 959 753h.

Secret Key Code (SKC) info - you MUST have the 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 VCDS.  *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.  Pictured below from mark1vws is the plastic tag.  If you cannot find this then you must retrieve the SKC yourself to work on the immobilizer or program new key chips!   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 tag with the key code on it (again, VW didn't give these after 2001), contact someone who has tools to retrieve the SKC from the instrument cluster, or buy a tool to retrieve the SKC.  VCDS software or the dealer cannot retrieve the SKC.

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 should 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, VCDS 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

-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 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 keeping the car running after 2 seconds.  

-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 and 1000q: constant low power or can't rev for more details.

More detailed information below is separated into immo-2 and immo-3 sections because they have different procedures.  I'm working on an immo-4 section, please refer to immo-3 and your bentley manual for now.  Remember, to work with the immobilizer, you MUST have a vag-com/VCDS tool.  You cannot use a generic code scanner, you must use a VCDS cable.  You can only use an emergency start without a VCDS and even then you must know the SKC code.

General troubleshooting procedures

1.  First, make sure the car battery is charged.  A low battery can cause problems with the immobilizer.  It also results in low cranking RPM during engine start - this will cause the ECU to prevent fueling and will let the engine not start at all vs. shutting off after 1 second.

2.  Try another key - you should have a valet key and second 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 antenna.  You can try reprogramming the chip with the procedures linked below.

3.  Check for error codes - scan the car with a VCDS 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.  This and the next solution appear to have something to do with a capacitor discharge or something resetting.  It sounds strange but many report that it works.

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.  Step on the brake pedal - this turns on the brake lights and discharges any stored electricity. .  This may reset the immo system.  Again, don't touch the cables to the battery, touch them 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.  Wiggling the key in the slot won't do anything because the range of the antenna/chip is about 1".

7.  Put a trickle charger on the battery, put the key to the "ON" position and leave it for a few hours.  If it didn't reset after 10 minutes it's been known to reset after a few hours and never appear again.

Model specific detailed information and procedures

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

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

Immo-3 troubleshooting and procedures (some 2002-2005/2006)

Immo-4 general information and troubleshooting (2005.5-2009)

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