Beau Waitforit Zagar

hi guys, i have a audi a5 b5 quattro 2.6 v6 and am in the middle of doing a engine swap to a 2.4 quad cam engine and i have lost my keys so am i able to buy a replacement key off ebay and code it in somehow or does audi have to do it

AudiMick

In the US we don't have immobilizers in our B5s, we also don't have 2.4 or 2.5 engines you may have to wait for someone with your car to chime in.

You can help by stating your model year and location.

twentysevenlitres

This could be fun!
Which ECU are you going to run? The original 2.6's, or the 2.4's?
I ask, as you may have incompatible plugs and components at the ECU end...

On your car the immobiliser will be a separate module under the dash. It'll be an off white box about the size of a cigarette packet above your right knee (on RHD cars, may be left knee LHD).
On post 97.5 cars (2.4 and 2.8 30V engine update - might have been post 99 facelift even) the immobiliser became incorporated into the dash module.
So the 2.4 ECU may not recognise the separate immobiliser module.
In any case, every module on the car (from climate, to dash, to ABS to cruise control) will have to be adapted to the new ECU via VCDS, or none of it will work.

It may be possible to switch the immobilser function off, but this will require the dash or immobiliser PIN code with a compatible ECU via VCDS (VAGCOM) - the PIN code is very difficult to find and is unique to each chassis. Vagtacho might be able to decode it.

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Bypassing all that for the moment, I'll assume you stick with the original 2.6 ECU...
The trick to the keys is to recognise the fact that the immobiliser is programmed to the transponder chip in the key - NOT vice-versa.
This changes your whole approach. A key shop can't program an Audi transponder, as there's nothing to program - they're all hard coded.
So you buy a key with the correct tranpsonder chip already installed. In your case it will be a Magamos ID13 for the '96 immobiliser box (if you update the dash, this becomes a Magamos Crypto ID48).
Get the key cut (might be hard if you don't have a key to begin with).
Then you need the PIN code for the immobiliser...
Get the PIN and you can program the key via VCDS.

Alternatively, you can spend $600 on having Audi make you a new key based on your chassis number...

Oneplank

One of these folks could certainly help

http://www.audiusa.com/content/dam/a...Facilities.pdf

They should be cheaper than the dealer. Not all locksmiths can cut Audi keys.