[ischmitz]

The DME is "matched" to the other control units in your car. In particular the DME hand-shakes with the immobilizer unit and talks to the alarm unit. You can replace an engine (assuming the new engine is the same type) but you can not mix and match components such as DME and other control units. All control units have the VIN number of the actual car in their permanent memory. To my knowledge all engine sensors and actuators on the 996 engine are dumb - they do not have any VIN-specific information. They simply provide signals to the DME or receive signals.

The issue comes up when someone wants to upgrade from a 3.4 to a 3.6. This is when the DME and sometimes the harness needs to be changed and that causes a rat-tail of other issues.

Ingo