Multi Function Display (MFD) only shows Toyota Logo

Can anyone help me with my problem, please? My MFD now only shows the Toyota Logo, whatever I do. Also, I cannot play music. The trick with pressing (hold) INFO and headlights three times does not bring up a diagnostic screen. My theory is that the MFD is waiting for some signal over the network before showing the usual screen (and it never gets that signal). Some years ago, I had a third party fit a new audio tuner and player (non-Toyota), and that worked more or less fine for years. They had to leave the old faulty Toyota audio in the circuit to make it all work, and they said to leave the graphic equaliser on even settings, and then forget it. The old Toyota audio CD changer had failed, but the rest was OK. My 'guess' is that they had to leave the old audio device connected because it terminates the AVC-LAN with a 60 ohm resistor. Maybe that connection came off, and now the LAN signals are not good, and the MFD is locked up 'always waiting' for the signal from an ECU.

Naturally I don't want to pay a dealer for a very expensive solution, so I would be grateful for any hints. I've searched the Web and cannot find any problems just like this reported. The MFD is a 86110-47081. I did try changing it for a 86110-47230 and that had a completely blank screen - though I don't know if that was fully working anyway. I now believe that the 47230 would not work anyway without mods. My current guess is that even if I did those mods, it would only result in the screen showing the Toyota Logo anyway (though it might be nice to have the extra resolution).

Many thanks in advance!

 

Many thanks for the suggestion! However, I have already tried that for one minute... I hoped/thought that was long enough (though it might not be). Effectively the power was disconnected for a few minutes when I tried another (sadly probably incompatible) MFD, and when I put the old one back it still only have the logo. I think I will try checking if the LAN is terminated properly... I will also check for any obvious wiring anomalies... I might also ask the dealer if they have any ideas. They might be able to read some diagnostic codes.

 

I did some more testing today. I found that if I put a small resistor (27 Ohm) across the TX2+ and - LAN connections at the back of the MDF, the screen lit up with the normal screen! I was also able to access diagnostics by INFO + 3 parking lights! However, now I have the 'standard' MDF problem with no connection to AUDIO or GATEWAY, and the complaint about 'Check the A/C'. When I checked the resistance across TX2+ and - before adding my resistor, the resistance was 'about' 40 Ohms, so the extra 27 makes 'about' 68 Ohm, so I guess the LAN needs to be terminated properly so that the screen displays normally. I will ask the audio if this makes sense to them tomorrow.