V70: Gearbox Tg-81sc no comms - 2015 v70

[ymc30]

Hi guys I desperately need your help as I am running out of ideas

Foreplay:
I've bought a 65 plate V70 D4 with a failed engine (D4204T5) which is an 8 speed auto (TG-81SC). I also happened to have a working engine-gearbox from an accident damaged V70 - same engine/gearbox combo.

Last week I dropped the failed engine with the gearbox and put the working one in. I did NOT touch any modules I even failed to change over the TCM from the non working engine/gearbox unit (where the gearbox is supposedly was working)

The car started first time and was running OK although next day I had "reduced transmission performance" but after I cleared the DTCs it went away and the gearbox was working fine but I still had some TCM related faults but hey, who cares?!?


The fun bit:
Today I took the TCM from the failed engine/gearbox combo (which TCM belongs to the car originally) to get rid of the DTCs.

Disconnected the battery, changed the TCM, reconnected everything - since then the car could not see the gear position (Shift gear to P) and refuse to start.

No connection with TCM and strangely no comms with power steering. Also no gear selection symbol on the RH side of the speedo.
Please see DTCs attached.

Any help would be appreciated