S80 disabled by computer, need urgent help

[sylvesterp3]

Hi,
My mechanic asked me to help him fix a Volvo that's stuck in his garage and I am posting this on his behalf.
He has a S80 year 2000. The electric schematic is the same in Volvo 2001. There were issues with the car he was trying to fix and he disconnected the central electric module unit.
The car lost immobilizer after disconnecting the central electric module. Now the car is completely out of service and is locked up.
When connecting the battery the hazard lights blink and the radio works, without the ignition key being on.
No other components work, no power locks, windows, anything. Just the radio and hazards are on. It seems like the electric system is shut off and the computer is not controlling anything.
I know my explanation might be a bit confusing , but I am repeating what he told me.
Does anyone know how to help? or has any idea what's happening.