The Decline and Rebirth of an Multifunction Display (MFD)

This is largely a note of thanks to the PriusChat community as well as documenting my recent experience. Especially because it has a happy ending for no cost.

TLDR: pull the fuses and put them back in to do a hard reset on the MFD.

The car is 2005 Prius with navigation, we bought it new, and it has about 220,000 miles on it.

Over the last month or so, the behavior of the MFD got odder and odder. First, it was responding to button pushes very slowly and seemed to be connecting over and over again to my phone. My first theory was that the bluetooth connection was wonky. So, I deleted our phones from the Prius. Seemed to help briefly but I think that was wishful thinking. The display became less and less responsive until yesterday it went into a constant reboot mode. It would show the initial screen, then go to the consumption screen, and then flash off and then go back to the initial screen. Over and over again. Every few seconds. I was able to control the climate if I pushed that button at the right time. Then it would give me the climate screen few seconds to change controls. Interestingly, the temp up/down buttons on the steering wheel seemed to continue working. And on a longer drive, after about 20 miles, it just stayed on the consumption screen and stopped constant rebooting.

When we got home, I got on PriusChat and saw comments that odd behavior of the MFD could be a sign that the 12V battery is dying. That seemed reasonable because of the behavior on the longer drive. Left it overnight, checked the voltage on the 12V battery and it was spot on. So started reading and checking the prices of used MFDs on ebay.

Then I saw a comment somewhere in the forum that pulling the MFD fuses to check them is a good idea and somewhere a comment that doing that forces a hard reboot of the MFD and can fix it. I found the fuse list in this thread: MFD does not light up | PriusChat Note that the last fuse may have been ACC/B.

These fuses are under the dashboard near the hood release. Accessing them is a feat of physical prowess and mental toughness. At least for me.

All of the fuses were fine. And somehow I managed to put them back in.

And then the MFD started working perfectly. I've started the car three times now and done some driving. So far, so good.

My thanks to everyone who has given advice on MFD issues over the years.

 

That's an excellent point. This is the first time it has done this in 20 years. I think our last 12V battery change was in 2020.