2014 Prius Speedometer & "Hybrid Sys Indicator" Displays turn off while driving...

Hi:
I've owned a 2014 Prius Four (not IV, Roman numerals were for model year 2010) w/o Nav for just about a year now. I've encounter this mysterious condition three times now where when I turn on my car, all I see on the front displays are the READY light on the far left and the mini-display that shows the shift pattern.
* Both the speedometer/fuel gauge display on the left of the shift pattern display and the "Hybrid status" display on the right of the shift postion display are OFF.
* The car operates normally (it's not in a limp-home mode).

When I first encountered this issue and reported it to my local dealer, they suggested I take a video of it with my smartphone. I did so the car (and a copy of the video) is now at the dealership.

The second and third times this issue came up, I took videos and did some additional testing.
- When these two displays are OFF, there is no backlight to the climate control LED display underneath the stereo...
- I normally drive the car with the headlamps in "AUTO" mode. When you shift the headlamp switch to "DRL off", the two missing displays automatically power on. In any other position (Auto, corner marker lamps only, or headlamps ON position) the two displays in question turn off.
- The issue isn't with me accidentally turning the dimmer switch too low. When the dimmer switch is set to max low and the dash light sensor is covered (emulating complete darkness outside), all three displays on the dash (including the shift position display) are barely visible/look off. As the service advisor saw in my video, that's not the case.

This is clearly a safety issue ("you cannot tell how fast you are going" and "you cannot tell easily how much gas you have left without going through the infotainment display) so for now the dealership at least seems to be on my side in that something needs to be repaired. The good news is that now that the issue has been documented in my service history, they did comment that it will get fixed eventually even if the issue comes back after test. For now, the dealership is stumped so they asked Toyota for guidance on what parts to try replacing.

My best estimate is that it's a control issue (something is interrupting power to the climate control backlight and the two displays seems to be cut) and/or a sensor issue vs some problems with both screens.

Q: Has anyone heard of a similar issue and if so, what parts were replaced?

Regards,
-g

 

In case any of you wanted to watch a video prattling on about this bug.
Anyone?

 

Dimmer switch just makes the activated displays lighter or darker. It could have some weird transient problem but if the problem was isolated to JUST the dimmer switch, all three displays would be lighter or darker. In my case, the shifter pattern display is sufficiently bright but the other two are OFF.

Something, whether it is the dimmer switch, the stalk, or the ambient light sensor, is causing power to be interrupted to the other two displays while still sending power to the center (shifter pattern display). It's either in the power distribution side or some external control line.

I'm not the dealer tech NOR do I have the wiring diagram for this car. If I was a betting person though, I would guess it's the stalk and/or something downstream of it on the control side because changing the stalk definitely turned the problem on/off.

Therefore, either power isn't getting correctly routed to the displays in the DRL, autolamps, or headlamp ON modes -or-
something is getting bunk data and not sending the right brightness control to the two displays.

This could be something as easy as a loose wire in a connector to the displays.
Either way, it's the dealer's problem.
-g

 

As per my original post, your suggestion doesn't explain why the center "shift pattern" displays stays fully lit while the two others disappear.
-g