possible to Sync IMMO and ECU on S60 II Denso ECM-U042600

[RobinPe]

I have an S60 II with a faulty ECU that has stopped communicating entirely, but I’ve found an identical replacement unit; however, I don’t know how to synchronize the control unit with the immobilizer.
Am I missing something here? Or not possible?

BR Robin

[T5 T6 Schnappi]

@RobinPe What happened to the car before the ECM went out? And what kind of diagnostics have been done to come to the conclusion that the ECM must be damaged? As this is really unlikely to be the problem here. Did you check the connectors for water ingress/corrosion? Did you check continuity/grounds/voltage supply/fuses/relais towards the ECM and CEM?
Syncing a used ECM from another car is impossible via OBD/software as the VIN specific, unique security/encryption pins for ECM and IMMO data can't be overwritten once they are programmed to a new unit at the factory or dealer. At least that is my current state of information.
Swapping the flash memory of your old ECM to another one on the bench would be required, hoping it isn't corrupted or damaged. Or you need to "virginize" the ECM from the donor car and than clone the software from your old ECM, or perform a software reload with VIDA.
Try to contact some local specialist for ecu repairs and ask them if they know this ECM, and if they can help you in any way if you really think the ECM is dead.