Nissan primastar problem
 

I have a intermittent immobiliser fault on my Nissan primastar 2004 1.9. The light on the dash stays on and doesn't go out. I have had the ecu and the body module tested and came back ok. I have checked wiring around gear box and to injectors and checked the obvious. Now and then when I turn the ignition it starts but most of the time it doesn't. Can anyone shed any light or have any other ideas. TIA