temperature sensor (TC0D and TC0P) shows -127°C

A negative value like what you are seeing is either, an unused sensor input, a bad sensor or the connection pathway is broken to the sensors input within the SMC logic.

Linux is really not the best way to diagnose your system. You should use either the CD/DVD diagnostics or the onboard diagnostics. Locate your original grey CD/DVD (grey disks) for the one with diagnostics. Or, see if the onboard works, restart your system and press the D key on your wired keyboard.

Reference:

• Mac startup key combinations
• Finding Hardware Faults: Exploring AHT & Apple Diagnostics
• Apple Hardware Test (AHT)

TC0D & TC0P - Are not listed within your systems service guide or within the schematics so I think these are not used call outs.

You talk about not being able to start OS-X/macOS. Can you give is a better idea on what is happening (put the system back together and retest) If you remember describe what transpired when the system stopped working.