Immobilizer FAQ and troubleshooting for VW and Audi, with key replacement tips

Nov 29, 2015
Immobilizer FAQ and troubleshooting for VW and Audi, with key replacement tips
  • VW and Audi key, remote, and immobilizer FAQ and troubleshooting

    This FAQ article describes how the immobilizer system works, how to replace the smart key in your VW or Audi remote, and troubleshooting steps/and how to bypass/delete the system.

    The immobilizer is a theft deterrent system located in the instrument cluster, the main car computer, a radio frequency identification (RFID) transponder chip in the VW or Audi smart 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 VW 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 when you turn the key to "ON", (shown activated below) it has an immobilizer. This light comes on for a second but quickly goes out when turning the car on and all is normal. If it stays on, you have an issue.

    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 if you're in North America but here's 1000q: mk3 key programming FAQ anyways. Audi have the same immobilizer systems but in different generations than VW so the same general procedures apply.

    The main symptom of a faulty system or activated immobilizer is that the engine shuts off after a second or the yellow car/key symbol on the dashboard flashes. A very low car battery or car battery removal could also cause the immobilizer to become active. On rare occasions it's triggered for unknown reasons - see the rest of this page for troubleshooting. Below is a video demo of the immobilizer shutting off the engine. If it doesn't act like this it's not the immobilizer. See the starter troubleshooting pages.

    The immobilizer chip has a range of about 1" through plastic and about 3" when out of the key (bare chip). 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 almost certain that it won't shut off the engine if the chip signal is interrupted after a few minutes. (I didn't want to test it by driving around without the chip signal). If you want to be very 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. One 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, the old metal key can still open the doors and start the engine but the immobilizer won't let the engine run for more than 1 second. Because of this, when you reset the immobilizer, all keys must be present or else the old ones won't work as intended anymore.

    The first step in getting a new Audi or VW Smart Key / remote key fob

    The remote has 3 main components: the keyless entry circuit board, the metal flip key to open the doors and insert into the ignition, and the immobilizer chip which talks to the immobilizer. Each is a separate system. The immobilizer chip is glued in the flip key half and cannot be purchased from VW separately. You can buy them on ebay as the megamos chip. Each must be correct for the Smart Key to work as intended. For example, even if you buy a cut metal 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.

    Here is a mk4 key 1998-2009. As you can see, the immobilizer chip (white arrow) uses no battery - it's an RFID chip energized by the pick up antenna on the ignition coil.

    2010 and newer keys look like this. They changed the key to work with KESSY, the keyless entry and start system. Even if you don't have KESSY, the key still looks like this. The immobilizer chip is the long black rectangle soldered to the board. At this time, I have no idea where to buy the chip by itself.

    -If the car has no immobilizer you can program the keyless entry yourself and have a new key cut anywhere which does a "reverse cut" side milled key found on VW - Audi. Again, if your instrument cluster doesn't have the yellow car/key symbol you don't have immobilizer.

    -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 another new or used key to prevent the immobilizer from acting up. The chip looks like a small grain of rice, pictured above and below. Then you can program the keyless entry yourself. If you need a new metal key, just take the key apart and swap the bad switchblade key with a new cut 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.

    For generation specific information on keys including how to take them apart, refer to the links at the top or search this FAQ. Audi followed different generations but the articles will work for them.

    How to use a remote starter with an immobilizer equipped car
    Remote starters still require a valid immobilizer signal just like a regular key. If you buy a remote starter system, make sure it has the relay signal box approved for VW/Audi signals. You must place the key or just the half with the chip inside the relay box. The relay box is then hidden somewhere in the car. When you use the remote starter, it relays the immobilizer signal inside the hidden box to the antenna around the ignition cylinder ring and works like OEM. They will work with any 1998-present system.

    How the immobilizer works and immobilizer differences by year
    If you have the yellow car symbol pictured at the top on the instrument cluster, you have an immobilizer. When you turn the car on, the antenna around the ignition switch induces a voltage in the RFID transponder chip. When the key is recognized, the immobilizer module, part of the instrument cluster, sends a random number to the key. The module and key both do a simple calculation and if they match, normal engine starting is allowed. Immo 3 also tells the ECU to do a calculation. Because of this, you can swap ECU on immo2 cars but not immo3 or above.

    The three main types of TDI immobilizer are immo2, immo3, and immo4. VW up to 1999 sold in North America don't have an immobilizer. Cars sold in Europe or the rest of the world may have immobilizer 1. These used a separate physical immobilizer box. 1999-2000 should have immo2. 2001-2005/6 use immo3. 2005/6-present use immo4. Around 2010, VW keys changed their design even though they still use immo4. As of this writing, immo5 is only found on the newest Audi. 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 because the chip is different.

    Immo 4 uses no module - the immobilizer is a function built into multiple parts.

    As late as 2001, there were some B5 Passat that didn't have any immobilizer. All Jetta, Golf, and Beetle definitely had them by this point.

    Cabrio and Eurovans have no immobilizer warning light and the immobilizer module is a separate physical box from the instrument cluster.

    Telling the difference between immobilizer 2 and 3
    If your car is in a transition year and you're not sure if you have immobilizer 2 vs. 3, connect a ross tech VCDS to the obd2 port and access the immobilizer module. Go to measuring block 81. If you see your VIN number it's 100% not immobilizer 2.

    -If you have no immo - you can swap keys, ECUs, and instrument clusters without any special programming. This assumes that the part numbers and software coding (settings) are the same.

    -If you have immo2 - you need the SKC to use a new key or instrument cluster but you can swap the ECU without any special programming. 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.

    -If you have immo3 - 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 to a car (unless you swap out the chip with your current one). Again, the chip-key half is separate from the remote keyless entry half.

    -If you have immo4 - found on mk5 and mk6 Volkswagens and newer Audi. 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 to a car (unless you swap out the chip with your current one). Same restrictions as immo3.

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

    The cheapest and easiest way to get a replacement VW or Audi Smart key
    Because of the variation in build dates, immobilizer generations, and remote compatibility, the easiest way to get a replacement key is from the dealer. Dealers are 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. Some won't touch ebay keys.

    The cheapest way to get a new key from the dealer is to buy a cut key from an online OEM parts dealership and take it to the local dealer for programming. The online dealership can cut it if they have your VIN number. Regardless of the number of keys, they typically charge for 1 hour even though it really only takes less than 15 minutes of actual work. If they charge you for 1/2 hour, it's very fair. The smart key immobilizer must be programmed in person with someone who has access to the SKC. 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!

    The absolute cheapest way to get a new key is to buy the programming tools yourself, buy a cut key online, and when you're done, resell the programming tools. The initial investment in the tools isn't cheap and most people end up keeping their VCDS tool since it's so useful. If you can get the dealer to only charge a half hour for programming, that is the cheaper route.

    NOTE: The newest keys 2007+ on most VW models and all 2010+ keys use additional encryption on the immobilizer chips. As of this writing, there are no aftermarket tools to program the immobilizer key yourself. In this case you must to go to the dealer. Technically speaking, you can use a qualified locksmith as a result of a class action lawsuit about smart keys but these specialized shops are few and hard to find. Due to the expensive equipment they have to rent from VW, they're usually not any cheaper than the dealership.

    -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 VW up to around 2006-2007, you have immo4, your Jetta remote is either VW# 1j0 959 753p, or 1k0 959 753h.

    -If you have a mk5-mk6 body VW 2010+ your key is a new style and you can't do much with them since there are no aftermarket tools to get the SKC. Go to the dealer.

    How to disable or bypass the immobilizer system in your VW or Audi
    Long story short, you have to bench flash the ECU with new programming to completely delete the immobilizer system. The immo light will still blink but the car will always start.. If you have an immo2 car and know the SKC code you can do an emergency bypass so that you can drive to the dealer. You can also order bypass boxes online. I've never used one since I've never had to and they are reported to be buggy/not always work. If it was too easy and fast to bypass it wouldn't be a very effective anti theft device, would it?

    If you wish to remove the immobilizer function from the car you can only do this through a specialized chip tune. This requires you to remove the ECU from the car and ship it to KermaTDI where it's bench flashed and rewritten. When seeking an immobilizer delete, make sure to include any requested ownership information to verify the status of the car. As a bonus, they can also do a power upgrade at the same time. Here's their banner:

    Problems that are NOT related or caused by the immobilizer system
    -If the starter does not engage or the engine does not "turn over" at all, this is not an immobilizer problem. You probably have an ignition switch or starter problem. For mk3 and mk4 cars, see 1000q: starter FAQ and troubleshooting. For mk4 Passat, see 1000q: B5 Passat starter fix. For mk5 Jetta or Golf, see 1000q: mk5 starter.

    -If your car shuts off more than 3 seconds after engine start it has nothing to do with the immobilizer. The immobilizer shuts the engine off in the 1st second.

    -The chip inside the key does not have a battery or other internal electricity source. It's an RFID chip and is "excited" by the antenna around the ignition switch. Shaking the key or changing the remote fob's battery will not fix any problem with the immobilizer. Just look at the pictures above - there are no batteries for the immobilizer chip. In the case of the 2010 and newer keys, if the battery dies you just hold the key next to where the ignition should be. The RFID signal will still be read.

    -The immobilizer system has nothing to do with opening or unlocking the doors. The immobilizer will not be activated by the alarm system - the alarm system affects the starter. The immobilizer's ONLY action is allowing the engine to stay running a second after starting it. Again, the keyless entry and immobilizer are separate.

    -It 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.

    Basic immobilizer troubleshooting

    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.

    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 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. Disconnect the battery negative terminal and step on the brake pedal - this turns on the brake lights and discharges any stored electricity. This may reset the immo system. I've heard that disconnecting BOTH negative and positive terminals of the battery and then touching the cables to each other only, while not attached to the battery can also reset it. I think that it takes more time and does the same thing as disconnecting the negative side and turning on the brake lights. 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. You could try wiggling the key in the slot in case there's a problem with the pickup coil. However, the range of the antenna/chip is about 1" so it's definitely not a range problem.

    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.

    Secret Key Code (SKC) info - you MUST have the SKC to work with the immobilizer!
    This exclusive content and the information below can be viewed in this post for premium members only. Once you have joined the forum, upgrade to a premium membership. Here is how to upgrade: This is all advanced information so if you don't want to invest the time and energy in getting tools or DIY troubleshooting, take it to the dealership. You can also ask in the forums with a free account.

    Advanced troubleshooting procedures

    Model specific procedures and differences between immobilizer systems

    The rest of this is in the exclusive content forum, join our community today!

    Update from Keithuk, 14 Dec 2014 from Ross-Tech forum.
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