06 supercharged, 75000 miles, either very urban or very motorway.

Recently the dash has shown “Transmission Fault” messages with a bong. The car continues to drive normally - no limp mode stuff - and the messages self clear after a few seconds.

I thought on a long motorway run I could detect a thrum thrum thrum vibration around 1500 rpm in 6. Haven’t been able to replicate it.

So I took it to a transmission specialist. They could get the “Transmission Fault”’message but couldn’t detect the thrum. Put a new battery in it just in case, but it’s still throwing up “Transmission Fault” which self clear almost immediately and do not affect the car.

The specialist pulled the following codes up:

TCM:
1 P0850-00 Park/neutral switch input circuit (Historic)
2 U0155-87 Lost communication with instrument cluster control module (Permanent).

Any ideas what’s going on?

TIA Range Rover 4.2 SC
AM V12VS
Porsche 991.1 Turbo S
Mini JCW conv