ME 7, CAN ID Catalyst temperatur - somebody knows the ID ? I can not find it in the Bosch FR. thx

okay. thank you. how can i replace it ? need to modify the ECU BIN and reflash yes ?

Yes, you will need to reflash the ECU. The change would be done through Assembly

What car is it and for which application do you need this variable on the powertrain can-bus ? Do you have a gauge or a monitor that is hooked on the can-bus or are you retrieving variables through the OBD2 protocol ?

You would need a tool that support MED9.1 ECU to read / write. If the ECU is matched to your car, you won't need to resync the immobilizer. Cheap tool would include MPPS (obd2) or Kess clone (boot). There might be some alternative for bench reading under 200usd

Disassembly would be done through IDA or ghidra (free), they both support PowerPC (MPC5XX). I do believe there is a guide on this forum regarding memory scheme, you can also validate if it matches with the memory_segment in the .A2L file

To get a better understanding of the variables, there is a MED9.1 Funktionsrahmen out there. You can also refer to this link for the MPC5XX instruction set  : https://www.nxp.com/docs/en/reference-manual/MPC82XINSET.pdf

If none of it speaks to you, all the resources are out there to learn it, or you can pay someone to do it