it is a code that wont be picked up by tech2's or any other vxhall obd2 interface, that code only appears on generic code readers and it is completly useless
if the light is not on then the code is not active as well
if the car hasn't had its timing chain done then it needs to be done as every vectra B had the old style gear and jets and it could well be the chain
benny is the man to replace chains and he does it for a fraction of the price, u can pm him