OK, since you also asked in public, I can as well also reply in public
There are two ways of doing this, complementing each other. First, you need to have fully and properly disassembled bin for your ECU, such that you know all memory cells are referenced properly and that you have found all the references to all cells, especially the CPU register area. Then you take the docs for the CPU, find the ADC input register addresses and do a search in the code to see if they are used. Sometimes you will see that an ADC channel is read, stored in another variable after clearing the control bits, but then that is it, the data does not travel anywhere. But then it also has to be connected on the board:
From the hardware side - you take all connector pins that are not connected on your car and/or are no described in the pinout diagrams for your car, you open the ECU and try to trace these pins down to the CPU, if they end up on the ADC ports you have likely candidates.
Then you log the suspected unused channel port addresses, apply voltages to the suspected pins and see if you trigger any changes.
