While on the return leg of a recent road trip the 12.3-inch multimedia central went dark. Every day for the last two years and throughout most of the road trip this past weekend, the multimedia display paired seamlessly with my Samsung Galaxy S23 Ultra via Android Auto. The multimedia display cycled easily through Google maps, Spotify music and podcasts, voice phone calls and received text messages.

Approximately a week before the screen went dark during the road trip, at start up, the car would require that I cycle through the selection of Android Auto and then select my phone before it would commence operating normally. It did not require me to re-pair my phone via Bluetooth with the car, I simply had to re-select my phone from the drop-down menu. Until last week, I made those selections over a year ago and they were stored in memory and were automatic. After the display screen went black, I tried several things to diagnose or fix the issue. Initially, while I was on the road, I disconnected my phone, restarted and re-connected it. When that didn’t work, I headed into a rest stop and turned off the car and then re-started it. Upon re-start I noticed that the climate control status bar along the bottom of the central multimedia display lit up, displayed its information and then the entire screen went black again. A bit frustrated, I went in and grabbed some food. Upon my return I started the car and put it in reverse to leave the parking slot. The central multimedia display nicely displayed both the back-up camera view and well as the front camera views…and once I had pulled out of the slot, promptly went dark again. Once I got home, I started the car and checked the Bluetooth connection from the phone side of the pairing, the phone was no longer automatically paired to the car. I went into the phone pairing menu and tried to re-pair it to the car but no go.

All of the above leads me to several conclusions (1) the display itself functions, deduced by the fact that it receives power and displays input from both cameras and climate control; (2) the display is not receiving signals from my phone via Bluetooth; (3) my phone continues to be able to seamless connect via Bluetooth to a myriad of other devices without difficulty. As such I think that there has been a slow failure during the prior week somewhere in the car’s Bluetooth control module unit. Can anyone describe where that unit is, and where its associated fuses, are located? Also is there any way to test it for functionality and if so, how? Does anyone have a part number for the Bluetooth control module on the 2019 E450? Am I missing another possible source of this issue? Thanks in advance.

 

It sounds like the main computer, the head unit, is failing. The Bluetooth module is integrated into it, not a separate box.
The screen works, but the brain behind it is crashing. The need to re-select your phone was the first sign of its software or hardware glitching.
A hard reset is your best first step. Disconnect the car's battery for about 15 minutes. This can sometimes reboot the system and clear the glitch. If that doesn't work, the head unit itself likely needs diagnosis or replacement.

 

Thanks, for the reply. It is very much appreciated. Well, this is going to be unpleasant. I was actually hoping that it was just a module. Ok time to look on the bright side, if the hard reboot doesn't work and I need a whole new head unit maybe I can upgrade to one with an actual touch control screen that uses the full display in Android auto...