VR6 won't start

[maxmc2]

Car was running fine last week when I put a new battery in it, went to start today and car starts then immediately cuts out and the oil light flashes, I've over ridden the immobiliser with the fob and tried a different key but doesn't change anything, any ideas where to start?

First thing i thought of was water ingress into the ecu after all this bad weather, hope not.

TIA