My Intermittent Immobilizer

Discussion in 'VW Mk4 Jetta, Golf, New Beetle, Passat TDI forum' started by Dudley, Jul 30, 2011.

  1. Dudley

    Dudley New Member

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    Hello, VW Brain Trust! I'm new to this forum, partly because my two TDI Golfs have generally behaved well. However, the 2003 is giving standard Immobilizer trouble: the engine catches then dies, and the key icon flashes. It does this no matter which of the three original keys I use. I generally cuss at the car (in German), wait a while, and eventually it'll start. Then it behaves normally for a few weeks. I'm tempted to suspect that it has a consistent number of successful starts before a bad one, suggesting a corruption in the rolling code cycle, but I can't keep track well enough to be sure. Also, in recent weeks, it appears to have been misbehaving more often.

    I'm slated to be at the dealer's on Aug. 1 for diagnosis, $100 just to sniff at it a little. I'd like to be more informed before I go there. For one thing, the dealer says the Immobilizer cannot be gotten rid of. True? Given that it acts up during only one start in 10 or 20, is there some culprit that is more likely than another? I've read somewhere that certain male & female terminals are of mismatched materials; I gather these would be where the key-reading antenna leads connect to the processor. Use of dissimilar contact plating is a poor practice, something we don't do in aircraft. Can somebody confirm that VW chose to do this on some cars? If so, has anybody tried Stabilant 22 or a similar active conductor solution at those interfaces? Since my car was assembled in Brazil, should I be cussing at it in Portugese?

    Thanks in advance for whatever learnin' you can send my way.
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  2. chittychittybangbang

    chittychittybangbang Administrator

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    The immo can be deleted w/aftermarket chip reflash. Not something the dealer can do or would know about. You would have to contact a tdi chip flasher for details and they won't share exactly what they edit since it's what they charge for.

    It's very unlikely the problem is in the key but it could be a bad contact. The immo is in the instrument cluster, the antenna is around the ignition cylinder. There isn't much wiring to get messed up but sometimes yes, the antenna does go bad.
  3. Dudley

    Dudley New Member

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    Thanks, Chitty. Any idea what there is about the antenna, AKA reader coil, that can go wrong? Passive devices don't usually have many failure modes.
  4. Dudley

    Dudley New Member

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    Update about immobilizer

    Today I elected to have the VW dealer look into the Immobilizer misbehavior, which pretty much means they read the VAGCom and told me what codes were stored. I don't think there was any further investigation (but they did wash the car!).

    There was, surprise surprise, a code for a failed reader coil. The coil is apparently integral to the ignition switch assembly, so you have to change a bigger piece than expected. It's $91. Labor is another $100. The part takes two weeks to arrive. I think I'm just going to take the suggestion given above and have a chipper delete that feature from the ECU firmware, rather than pay more to keep an unwanted system running, and possibly have it act up in the future.

    However, before I send out the ECU, I intend to try some Stabilant 22 on the reader terminals. It might be interesting. I figure the self-test algorithm can't discriminate between a weak antenna and a troubled wire, and with the signal operating near 300 MHz, trouble with the terminals would be problematic. It's worth playing with.
  5. chittychittybangbang

    chittychittybangbang Administrator

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    Thanks for the update, and I don't know why the coils fail but they do. :dunno It's a VW :D

    A chip can also improve the power levels of the car safely and hopefully it'll put a smile back on your face!
  6. vw709

    vw709 New Member

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  7. chittychittybangbang

    chittychittybangbang Administrator

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  8. Dudley

    Dudley New Member

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    The dealer didn't specify whether the ignition lock/switch assembly was ordered to match existing keys, but then I didn't ask, mainly because I didn't know how much stuff you get for $91. For that little money I kinda expected the installer would transplant the old key cylinder into a new body, but that's only a guess.
  9. Dudley

    Dudley New Member

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    Next update - following the helpful video from elsewhere on this site, I removed the ignition lock cylinder, just to make it easier to access the reader coil connector. It was pretty easy. Once the thing was on the bench, I gently dabbed on some Stabilant 22 on the terminal pins (they're male pins at the reader coil, easier to apply the stuff there). I reassembled the cylinder in the car, and right away got a half-dozen successful starts. That does not guarantee it's fixed, but it's a good beginning.

    I haven't dug out the dash cluster yet to treat the pins at that end of the harness. Theoretically they are just as vulnerable to trouble.
  10. chittychittybangbang

    chittychittybangbang Administrator

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    Nice tip, I will add the stabilant 22 tip to the immo faq article. What is stabilant 22 do exactly? Did you clean the contacts otherwise?
  11. Dudley

    Dudley New Member

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    Stabilant 22 is a "contact enhancer". It's much more sophisticated than old materials like copper paste, and its relatively low viscosity makes it practical to apply to physically small structures like IC sockets. It fills the micro-scale voids in contact pairs with a film that becomes conductive when excited by a passing current. You can read up at www.stabilant.com.

    No, I didn't even attempt to clean the terminals. They are hard to get at, and any attempt at cleaning would probably make things worse.

    My basic theory is that the wiring and, especially, the terminals are poorly suited to conducting RF energy. It's not the same as a simple DC circuit. Proper RF terminals are much higher quality than these common square pins. It's not surprising that a signal burst generated in the dash cluster would have a hard time getting to the coil. Stabilant goes a long way toward remedying the problem.
  12. Dudley

    Dudley New Member

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    Further update - Harumph. I've been driving the car normally for two days, and the immo acted up twice. The symptoms are apparently just the same as they were prior to my simplistic "repair". If the reader coil is working any better, I sure can't tell. I was motivated to try the contact enhancer by the VAG COM: the stored code said there was a problem with the coil (exact wording of the code is unknown to me). However, we mere mortals may never know just how discriminating the self-test process is. I'm glad I didn't authorize the changing of that coil & cylinder by the dealer; I'd have been out $200 and most likely the problem would still be there.

    I am not motivated to try much of anything else. I intend to send the engine control module out to a chipper who can delete the Immobilizer routine.
  13. Dudley

    Dudley New Member

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    Having decided to delete the immo, I took the ECU out of the car yesterday. Man, that's a fiddly kind of job. This car has an automatic transmission and therefore a tranny controller; I chose to remove the TCU for better access to the ECU. The ECU will be shipped out today, well packed and insured, and with luck I'll have it back by the weekend, with a very helpful case of memory loss.
  14. Dudley

    Dudley New Member

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    Results of Immobilizer Delete

    Well, I got my ECU back from the chipper today, and got it reinstalled. The car worked just fine on a few starts and test drives. I sure hope this is the end of immo problems!

    For anyone interested, I chose to have Malone Tuning in Canada do the immo delete. The cost was $50 (US dollars that is) plus shipping, seems reasonable to me. The whole process took eight days including postal time, no overnight freight services were used. I didn't opt for any performance upgrades.

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