Scenic 1 Immobiliser?

Hi everyone,



I'm new to this forum and promise that I've searched previous threads thoroughly before posting this.



Basically I own a very tidy late 2002 Scenic with both original keys (one virtually unused). Both keys unlock the car no problem. However when you turn the ignition, the immobiliser light in the dash goes out as it should but the car won't start (just turns over). Sometimes if you lock and unlock the central locking a few times, the car then starts (though this might be coincidence). This problem has been going on for ages but has become a lot worse (starter motor and TDC sensor both replaced before I realised it might be immobiliser).



With one of the ignition keys, if I leave it turned 3/4 way in the ignition for a minute or so (without trying to start the car) so that all of the dash lights are on, it will then start successfully. The other ignition key has recently had the battery replaced and this trick doesn't work with it.



Sometimes both keys will start the car without difficulty.



Does this sound staggeringly familiar to anyone?



Thanks



Brett