Cannot see current mpg on navigation screen and odometer

Can you see the speedometer, gear selector position, etc?

Where are you reading the battery voltage when the car is off?

 

It sounds like the combination meter (CM) has failed. That's fairly common, and Toyota issued a nine-year warranty extension that has expired for your car. Some eBay vendors will repair the meter for about $100, but you need to do the removal--a few hours the first time, 45 minutes the second time. Basic small hand tools, and you need to remove the PS air bag so be safe.

The car can still be driven, but mileage won't be logged, and no fuel gauge. You might have to hold the button down for several seconds to get it to turn off. Use a nav device for speed. And I think the rear hatch won't open.

The failure is usually intermittent and usually on cold days. It may come back for a while at times.

 

Although, this thread's topic is slightly different to your Prius' problem, take a look at it anyway:

Combination Meters that stop at 299,999 miles, Who's affected and what you can do about it.

Your model year is one that is affected by the 299,999 mile limitation, so you may want to consider retrofitting a 2006-2009 combination meter (CM) to your car, with which Matt can help. (You also need to change the light cluster for one Matt has modified to make this work).

In any case, Matt at Texas Hybrids can repair your current CM. His price is competitive and I would trust him over a random eBay seller (even though Matt advertises there too, I think lol). You don't say where in the US you are, but I'd send my CM there from any state. YMMV.

Hope that helps.

 

These are all symptoms of a failed CM. The only options available to you, if you want it fixed, is to have Toyota replace it for $1xxx or remove it yourself and send it to be repaired at a place like Texas Hybrids for around $150.

 

it is an issue, but not the issue. I don't believe they are related, but that issue needs to be addressed as well.