My Intermittent Immobilizer - VW TDI forum and Audi TDI forum

Dudley · #1 07-30-2011, 10:03 PM

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.

chittychittybangbang · #2 07-30-2011, 11:22 PM

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.

Dudley · #3 07-30-2011, 11:39 PM

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.

Dudley · #4 08-01-2011, 11:23 PM

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.

chittychittybangbang · #5 08-01-2011, 11:57 PM

Thanks for the update, and I don't know why the coils fail but they do.

It's a VW

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

vw709 · #6 08-02-2011, 07:58 AM

http://www.myturbodiesel.com/1000q/m...er-removal.htm Here's the article on ignition switch replacement but how do you get the new lock cylinder to match the key? Or would you have to buy a new set of keys? If so, that is a major pain!

chittychittybangbang · #7 08-02-2011, 02:40 PM

Quote:

Originally Posted by vw709

http://www.myturbodiesel.com/1000q/m...er-removal.htm Here's the article on ignition switch replacement but how do you get the new lock cylinder to match the key? Or would you have to buy a new set of keys? If so, that is a major pain!

I believe the new ignition switch is special ordered with the correct tumblers.

Dudley · #8 08-02-2011, 07:02 PM

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.

Dudley · #9 08-03-2011, 08:14 PM

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.