Immobiliser issues

[S3PGA]

After a long period of storage this is the year my S3 is finally getting back on the road but I've encountered a (hopefully easily fixed) problem.

I've fitted a new battery and started her up without any problem. Backed out of the garage, washed, waxed and generally got her looking how she should.

The battery was slightly too wide for the tray due to the plastic flanges at the bottom so I disconnected, ground them off and refitted it.

All good until I tried to start up again but the immobiliser (Meta M36) refuses to disarm. The alarm (Meta M99) works fine and arms/disarms using the key fob but the little black dongle won't switch off of the immobiliser. Same happens with both sets of keys and fobs.

I've had a search and tried a few suggested fixes such as disconnecting the battery for a couple of minutes, re-registering the fob with multiple presses and confirmed all the cables I can find are firmly connected.

Really hoping someone here can offer a few words of wisdom and I can get her up and running ready for an Mot.

[Chim450]

If you've tried all those things with no joy, then it seems likely that the immobiliser is probably at fault.
Had the battery been flat for a long time whilst the car was in storage? Apparently the immobiliser can suffer when this happens.
You could try bypassing the immobiliser.

[S3PGA]

Thanks for the reply.

The car had been sat for about 3 years but since the new battery I had started it half a dozen times without any issues. It's only since the battery was disconnected yesterday that the immobiliser has decided not to behave.

I've just read that it is possible to reprogram the dangle so will look further into that. If not then I think you might be right, thankfully a replacement unit isn't too expensive.