2006 throwing up service lights

You can start by getting the codes that you are able to get without any scan tool.

Blink (a/k/a Flash) Codes – How to. | PriusChat

Then at least you will know which codes those are, while you work on how to get the rest of them.

 

Car details, recent maintenance/accident history?

 

The blinking light code will need a source to tell you what the issue is as well as understanding the blink rate. Easy to do but be careful using a paperclip to short between sockets - make certain to count carefully.

Higher end code readers but well under $200 are well worth the cost. They can read codes and also freeze frame to isolate and tell you what is causing the code in more detail. Get one from amazon with next day delivery. Codes can then be looked up on line or buy a repair guide (extremely useful for minor repair issues, anyway) to get details on the code relative to your model.

These will pay for themselves many times over because an old Prius will be throwing codes again and again in the future. Knowing what to fix and even ignore can save $$$. Some might be easily fixed by yourself rather than a shop.

 

Hmm. In the era when the MFD display was designed LCD backlights were usually small fluorescent tubes on two opposing sides of the display, run off a high voltage power supply. As the tubes age the power supplies can draw substantially more power. This is based on computer displays, assuming it is the same here. Among other things this often resulted in failure of the electrolytic capacitors in that supply, which would eventually, puff up or leak. I suppose it is possible that the MFD is now drawing so much power it is affecting other systems, although I would have thought a blown fuse would be the outcome, rather than the dash lighting up. Another possibility is that the 12V system is running at too low a voltage. If the OP has a voltmeter perhaps check the voltage between the jump post in the fuse box under the hood and any nearby bare metal (the bolts on the edge of the inverter work.) If that isn't at least 13.5V with the car on then there is a problem with the "12V" system and that should be investigated.

An OBD2 dongle and some software is still needed though. There are probably codes right now, and they will give a much better suggestion of what might be wrong.

 

The lights and trouble codes don't lie, but are often misinterpreted by people who don't look up the full explanations of what they mean, or who make dubious assumptions like "brakes work fine → brake codes can't have anything useful to tell me".

Most of the codes are intended as warnings, so it isn't surprising that they often appear before the driver notices an issue. If they only appeared when you already knew there was a problem, they wouldn't be warnings.

The conditions to trigger the warnings are in many cases very specific and elusive, and usually required to come up in two consecutive drives to trigger the warning. So it also isn't surprising that sometimes when you clear them and pass up that first opportunity to deal with whatever issue they were reporting, the next opportunity may come weeks, months, or sometimes years later.

The brake system in a Prius relies on a properly-functioning hybrid system to handle its part of regen braking and traction and stability control. For that reason, the brake system will always report trouble codes when the hybrid system does. However, the only way to know if those are the only brake system codes you have is to read them.

The triangle comes on for around two hundred distinct trouble codes, only some of which have anything to do with the battery. You mention knowing that the triangle is about the battery in your case, but you didn't say much about how you know that. That information would help us give you better advice. And really, the best way to help us give you better advice is to post the actual codes: not paraphrase descriptions or what somebody somewhere thought they meant.

The source for what the blinked code means is the same repair manual where you would look up the alphanumeric codes from a reader. How to understand the blinking is, of course, in that manual too, but also fully explained on the PriusChat wiki page that was linked above, which also explains the easy way to find those codes in the manual.

Looking up the code meanings online is always dicey. Most of the codes fall either into the manufacturer-defined categories or into the industry-wide categories where they are assigned by SAE. (Many threads here on PriusChat have more detail on that, and how to recognize codes in those different categories.)

A manufacturer-defined code can mean completely different things in cars from different manufacturers, or even different models from one manufacturer. Those are the ones where, obviously, you have to look in the repair manual for the car model you have, and ignore with extreme prejudice everything you may find online that is different.

The SAE-standardized codes sound more promising. The good news is, you can search those online and at least the one-liner fortune cookie descriptions that come up will be right. The bad news is, they'll be so generic—"Throttle / Pedal Position Sensor / Switch Circuit B" is one actual example—that you still have to go to your car's repair manual to pin down what actual part of a Prius is the one Toyota decided to identify with that SAE standard name.