Hello frostbite
Have you tried using one of the other blue keys that came with your car? That would be my first check, it would prove the condition of your key's immobiliser chip.
I think i would check in this order;
1.Spare blue key or try copy of your blue key's chip.
2.Aerial wire check/change
3.Immobiliser itself and its wiring. (maybe check earth points in the cabin under the dash)
This is the imobiliser aerial/reciver wire
The loop end goes over the key barrel. and the connector goes into the immobiliser box. You could check it for damage, check it's physical position is good, and could try cleaning the electrical contacts. I noticed from reading the forum people have had to replace these aerial wires in the past as a solution.
In England a copy of a Bravo imobiliser Key costs about £25 which is not too much money and it takes minuits.
The Bravo's immobiliser system is made up of 3 parts;
1.The chip that is inside your key
2.The black aerial/reciever wire.
3.The immobiliser electronic box, that is matched to and communicates with your cars ECU.
This is a picture of the immobiliser chips inside the keys; Ignore the PCB (printed circuit board) that is just the remote central locking and a utterly seperate system. The key's chip at the top is from a Mk2 1998-2001 Bravo it is a black flat and almost rectangular a more modern style. At the bottom is the Mk1 1995-1998 immobiliser chip and it is brown shaped like a capsule or pill.
I can say my immobiliser turns off much much quicker since i had my original pill style chip copied to the more modern black rectangular style chip.
Sorry for the long post hope it makes sense and good luck
