MFD Black Screen, No Audio on 2015. Puzzled.

Issue background information:

I have a 2015 Persona. Yesterday upon starting the car the issue began. It worked a few days prior. Figured it was a weird bug and would go away upon restarting the car but no dice.

What happens is, I start the car, the Toyota logo pops up on the MFD, then it goes black (but can still see backlight). No radio playing. If I shift in reverse, backup cam will flash up for half a second (indicating that something is partially working and the screen itself isn't borked) but then switch back to black. I can do this multiple times and it flashes up with the reverse cam feed briefly every time. I can open the setup menu briefly which flashes away as well. If I turn the volume knobs, the little menu overlay at the top of the screen pops in and the volume changes with the scroll wheel.

Attempted troubleshooting so far:

1. Reboot the car. Tried multiple times turning fully on and off. Left overnight, no dice. Tried booting into "accessory" mode (2 clicks, no brake pedal) and same result.

2. Disconnected 12V battery for 5 mins. Lost my clock setting and trip meter reading indicating that the battery was disconnected long enough to erase system settings. Only difference was it looks like it tried to boot the MFD twice (Toyota logo came up, then black, then Toyota logo again, then back to black) which is the first time I saw that.

Questions:

1. Does anyone have any experience with a similar issue? I tried to search this forum and Reddit and came up with some people with dead MFDs but nobody with this exact set up symptoms.

2. Could this be a symptom of a dying 12V battery by any chance? The 12V battery is original to the car. Should 12V replacement be my first step?

3. If above 12V swap does not work, assume I should try to replace the head unit?


Happy New Year and thanks in advance to anyone generous enough to take their time to help me out.

 

Alright! So spent a few hours today and I now have a diagnosis and a solution that restores 80% of the desired car features for my typical use case. Updating this thread for posterity.

Today here is what I did, starting with the things that didn't work. Went from least effort to most effort in my troubleshooting in the interests of time.

1. Pulled radio fuse (28, below the steering wheel), fuse is intact. Left out for a couple minutes and then plugged back in. This appeared to reset the radio similar to when I disconnected the 12V battery, but no improvement with my issue.

2. Attempted to update my software from the official "Toyota Software Updates" site which told me that my Prius had a software update. Downloaded and placed on a newly formatted flash drive as instructed. Plugged into my car USB - no dice.

3. Investigated the USB port for curiosity. The USB port is powered from the radio. Specifically from the entension box in 3rd gen Priuses with navigation. Plugged my phone in to charge, which was constantly disconnecting/reconnecting the charging status, every second it would flash on, then off. Curious. Time interval matches up with the brevity with which the backup camera and setup menu would flash on the screen for when triggered.

4. Pulled my radio. Lost one of the four 10mm bolts that holds it in somewhere in the guts of the Prius - oops. Checked all wiring connections, including unplugging and reconnecting. Nothing.

5. And trying a different radio wiring config, voila...

The verdict: failed extension box. The extension box is made by Harman, and is included on Priuses with navigation. It is bolted on below your radio. As far as I know it enables the "apps" section of the vehicle including maps and a couple other features like voice recognition.

Toyota generously offers this part for the MSRP of $1,216.76. Lol! Used on Ebay, you can get the entire radio unit including extension box, just make sure to match up the number on the bottom right of your radio with the replacement. For my 2015 Persona, the radio with expansion box is "57032." Used ones are selling for $200. One seller offers a 90 day warranty. So you could swap a plug and play unit, which may fail again in the future, or if you're cheap like me and want most of the functionality back for a fraction of the price:

The 80% functionality solution, for free or a few bucks:

You regain: FM/AM/SAT radio, CD player, AUX input, backup camera display, USB charging, steering wheel audio controls

You lose: Bluetooth, voice recognition, built-in navigation (along with other "apps" but does anyone really use these)

1. Remove necessary trim and the radio itself. Plenty of vids on YouTube.

2. Locate the radio connector harness on the Harman expansion box (wide plug on the bottom). Disconnect it. It splits into two plugs that connect to the radio. Disconnect these.

3. There's 2 plugs left on the expansion box: a gray connector (this is for USB power) and another one for GPS I think. Disconnect both.

4. On the radio, there's a gray blank connector. Remove this, and insert the gray USB connector that you removed from the expansion box into the radio. Leave the second small connector cable (GPS?) disconnected.

5. Startup check. The radio should boot now, since the expansion box is taken out of the circuit. I suspect whatever it boots to, is some primitive firmware version that the non-navigation Priuses have.

6. If it works and you're fine with what's been lost, reinstall the radio. I went to Staples and bought an AUX cable for $4.47. I can now connect to my phone to listen to podcasts and Spotify, which I previously played over Bluetooth.

I've got my media to listen to so I'm not driving in silence, and I've got my backup cam. Happy enough with the solution for the price. The only thing I will really miss is phone call integration. I haven't tested a call over AUX yet to see if the microphone on the phone is acceptable to pick up my voice and have a passable phone call — should theoretically work if the phone is mounted close to the driver with clearance for sound travel.

Suspected solution to regain Bluetooth:

You'll notice Bluetooth is totally missing from the Setup menu now. You can select it as an audio source, but no way to pair devices. I suspect this feature is moved over to the expansion box on Priuses with navigation, at least at a software level.

If, theoretically, someone could get a .iso of the software from a non-navigation 3rd gen Prius, I suspect that this could be installed to my radio and it would restore Bluetooth, as the radio unit for the non-navigation Prius appears to be the same. So it would just be like I "downgraded" the radio if that makes sense. Unfortunately this appears to be impossible to test as all software update files have been purged from the Internet by Toyota. There's no update available to download for the non-nav version on their site. Some users had posted the files years ago, but all links that I can find are dead.

But, maybe this wouldn't work by just plugging in the flash drive with the software file since it's not an update but a re-flash and reinstall. I'd like to try it, but am unable to due to not having the 3rd gen Prius non-nav .iso image. Maybe the BT hardware lives in the extension box on this radio, and they're not as similar as they look.

As it is now I cannot update to the newest "with nav" software either to see if anything is different on this fallback non-nav version, since a required step is going to the "Apps" screen and plugging in my flash drive. Since I have no expansion box, I can't get to the "Apps" screen. I don't know if the process is different if I have a non-nav .iso, or if I'd just be totally stuck because the "Apps" step is inherent to a software upgrade on the nav version. Oh well.

Thanks to forum user "gromittoo" who has posted a lot of info about the extension boxes on various threads.