Low engine oil pressure

The Blue Driver software is pretty extensive. It can describe the codes in detail and suggest the top solutions that mechanics have found. Just as a stab in the dark, I'd say the engine is running hot and causing the coolant pump to over-rev. Being down by 3-4 quarts will undoubtedly do that. The seriousness of the problem depends on how quickly the car drank that many quarts. 2 months/2,000 miles? That would be kinda bad. 6 months/6,000 miles? Not so bad. You definitely don't want to let it run so low on oil again. There's an even chance you already need a new head gasket. Unfortunately, no code says, "Replace head gasket."

 

Oil low and dirty in just 2 weeks -- did the first dealership actually do an oil change? It seems more likely that they somehow failed to do so.

Leaks are just one manner of losing oil, there are others. That is why regular oil level checks are required in between oil changes. When it gets down 3-4 quarts, you have gone far too long. See this recent thread for more details:
What's with exclamation mark sign? | PriusChat

This is just a special hidden trip odometer that is supposed to be manually reset at each maintenance. Technicians sometimes forget to do this. The Owner's Manual tells you how to do it. But whenever it does light up, do check when the previous service was done, to see if it is actually time for more.

I have no feedback on the various trouble codes, hopefully others will.

 

This is one reason I always check the oil myself shortly after fetching the car. This also tells me the starting level, which is almost never right on the dot.

If I was more proactive, I'd check right at the shop every time. It was such a time that I first discovered a nice wrench left atop the engine. Only after returning it did I also discover the oil cap was left off, sitting beside the filler hole. At that point, I felt I should have just kept their wrench. Regardless, I never did any more business with that shop (a regular stealership, back before the proliferation of quick change places, and oddly still in business).

 

I drain and fill the oil myself, and put in the spec 4.2 liters (4.4 quarts). Carefully measured with a 5 liter pitcher/graduate. And yeah I know about capillary effect, how fluids kinda curve up at the container wall.

Checking a day or two later, it's invariably about 1/4" below the top mark. I leave it alone, and so far it's never budged from there till the next oil change.

 

Did you not ever check the oil level during this time?

The gen III Prii are notorious for oil consumption as they age (at least in my experience and from what I heard). If you drive a lot (especially with severe conditions like mountain roads) then it is relatively "normal" for the oil level to drop below the low mark every two weeks. You need to check the oil level regularly, like every weekend or 500 miles, and add oil as necessary to keep the level between the two marks (preferrably closer to the top one, so it lasts longer, but try not to overfill either).

 

I check oil every other day and no burning yet, knock on wood. It’s near 150,000 miles w/100 mi daily commute & 13,000 mi oci. Let engine temp go up gradually then drive like a maniac is my best advice to minimize head gasket destruction.

 

Coolant pump over revolution:
When the pump impeller shears from the drive shaft, the pump motor is now unloaded and goes into free spin at high rpm and stops pumping any coolant. Replacements are available to be found, maybe amayama.com.

iPad ?

 

IIRC Amayama wasn't too competitive for water pump, but do comparison shop. It is a good source for Canucks, and sometimes their prices are very good.