Vx ls1 start when cold but dies secconds later

Hey guys just wondering if anyone could shead some light for me, i was driving to work after filling up the other morning and the car randomly died mid driving, i pulled over and it wouldnt start back up, i tried and tried again and id only get very small start ups before it would die again, i left it and came back after work to find it starting again which lasted around 30 secconds then it died again and wouldnt restart

I was leaning towards bcm/imobilser issue but i noticed that when pressing unlock on the key the security light would go out and everything seemed normal, i guess it isnt ruled out yet but i had a person connect a tech 2 to my car and it had no fault in the bcm, it seems also with a key twist the light goes away too

I had a friend who had a look and sugested that maybe my crank angle sensor was dead and thats why i couldnt start it apart from being cold, because if it was bcm i should be able to get it start for an amount of time after unlocking the car? I notied when i started my car last night too when it was alot colder that it seemed to stay on for a little longer then previous attempts.

Oh and too add if it helps a few weeks back id get an issue where my car would start and if i didnt put throttle on it would just die, dunno if its linked but figured id mention it anyway

Hoping anyone with abit of experience and advice can give some words. Thanks heaps guys!