Hello guys, so i've had this problem for a while now where the radio says "The external system is not connected" "NO AUDIO" and "Check connector for AC". The display is responsive but its pretty useless as i cant control the heat, music or navigation.
So far i have changed the display for a new used one, the disc reader module and the amplifier in the trunk. all of the fuses in the engine bay and footrest on both sides are intact. I have been to a toyota dealer hoping that they would get somewhere but they were pretty useless, they just checked what i have already checked. i've had the display out multiple times now and checked for loose connections or bad wires, the only clue i've got is sometimes when i tug on the wiring harness going to the right behind the display towards the glove box the display will shut off and the hazards will blink rapidly. not sure if this is some sort of anti theft feature but i have not been able to locate any abnormalities in the wiring. both me and toyota have measured the connectors going into the head unit. Im pretty sure this might be a LIN problem, as everything has power but somewhere the communication is being lost, but im struggling to find a good wiring diagram to fault trace on this.
It is winter here now and i cant use the car and im not very motivated to sit in the cold and fault trace with nothing to go on.

Fault codes B1248, B1205, B1262

Any tips or help is greatly appreciated, thanks in advance.