The immobiliser is mounted on the A pillar and is secured by two torx 5 point security bolts.
Access is difficult and requires removal of the lower dash panel and the bracket securing the diagnostic socket.
If the car has a sunroof one of the sunroof drains is located just above it and have been known to leak but as you haven't got one then this rules out as a potential cause of the problem.
If your immobiliser has given up the ghost I may be able to ressurect it if it's not too damaged
Russ