A4 B5 Immobiliser Woes

[wiliferus]

Hi folks,

Got a 1996 A4 Tdi 110 (AFN?). Been having starting problems with it for a while now, initially thought it was the glow plugs but replaced them and the problem persisted.

Managed to pin it down the immobiliser (i think)!

Basically on the dash when you half turn the key to fire up the electrics, there is a flashing light which is a car with a key underneath it. If this continues to flash, which it does often, if i try and start the engine it fires briefly and then dies.
If i repeatedly turn the key on and off until the light goes out and doesn't flash, she fires fine. I'm figuring this is def the immobiliser so would like to disconnect it. (its £800 worth of car so not worth fixing!)

Does anybody have any knowledge or experience of this immobiliser so i can snip a few wires and take it out of the loop? I'm sure its the factory fit type.

Many thanks in advance

[riverstyx]

I've owned my A4 less than a week so I'm by no means an expert on the car but from my experience with other vehicles immobiliser systems I'd be very surprised if you could disable the immobiliser that easily as they generally communicate directly with the engine ecu.

A couple of possibilities spring to mind:

- do you have a second key for the vehicle? if so does this exibit the same symptoms (ie rule out an issue with the rfid capsule within the key) - if you dont have another key it might be worth getting yours cloned and try that one.

- the will be a coil antenna near the ignition switch which is how the unit communicates with the key - I had similar issues to what you have described on my alfa romeo and it turned out the antenna had become detached and moved and was no longer close enough to the key to communicate reliably.

I'm sure others here will be able to give more specific information with regard to the A4, but this is what it would investigate initially.

Hope this helps,
Martin.

[DJJoker]

It is definately a key / coil antenna issue and is quite common for this model, I have the same problem and have tried different keys without success.

Most of the time turning it off and taking the key out and trying again works fine. I have also found that if the error is cleared from the on board computer using VAGCOM that it behaves a little better for about 3 months before getting worse again.

I haven't yet come across an easy way to fix this permenantly without spending lots of £££