If you are getting that fault in the engine ECU then it means that it hasn't received a valid code from the BECM.
This could be as simple as the passive immobiliser has kicked in and the engine ECU is saying that it doesn't have a code/won't let it start,
Or that the engine ECU and BECM have lost sync.
Or that the BECM won't let the vehicle start because it needs the EKA.
On a Thor, any time you read the engine ECU, and it isn't getting the immobiliser code transmitted from the BECM (or it's not receiving it, if there's a broken wire for example) then it will show this 'fault'. Once the vehicle is in a position where it will start (EKA entered, immobiliser off etc, then the 'fault' will go away.
It could be something as simple as it's lost sync (if the vehicle is cranking, but not starting). Or it could be a lockout problem if the central locking/alarm won't switch off, and you get 'ENGINE DISABLED' on the dash. That fault won't help with what's causing the problem - it's just saying that the engine ECU won't let the engine start because it isn't receiving a valid immobiliser code for whatever reason.
