Well, I have located said module

(Being an electronic box, obviously the best place for Volvo to locate it is on the underside of the car next to the wheel arch (just behind the fuel filter)! Once I had established that this was the weak link in the electrical system I popped the top off and had a look inside. It was full of water ingress corrosion! (Where is the Smiley for "I cannot understand WTF they were thinking?" :/ )

I bypassed it and the car is now running.

A new module is about £300!

What is the purpose of this ECU?

The main ECU controls the relay and the safety related cut out if the engine is not running seems to be operate just fine.

WHY is there an additional ECU here that doesn't actually seem to do anything useful? What is its purpose?


(Appart from providing a future weak link)