Showered my engine bay with coolant, now Check Hybrid triangle

You really need codes.

What kind of code reader do you have? A bluetooth app?

Somebody reported O'Reillys Auto Parts had a hybrid capable scanner for customer scans.

 

P261B is the code for the water pump doing less than 900 RPM when it should be doing well above that. So your first feeling that the water pump was "laboring" probably was accurate, and you shouldn't have been so quick to have "realized pump was OK".

P0117's fortune cookie sounds innocuous enough: the coolant temperature sensor circuit is low, how bad can that be, right?

Except the Prius uses negative-temperature-coefficient thermistors. Their resistance goes lower the hotter they get. When it gets low enough to set P0117, that means the reading is so hot the ECM isn't even sure if it's a real reading or not.

But with you knowing your water pump isn't working, that's very probably a real reading that you should take seriously. Get the pump fixed and don't keep overheating the engine so much. That's probably what sprayed the engine compartment and what burst the hose.

There is a safety rule programmed into the ECM, such that when it has a known water pump code like P261B active, it makes its own effort not to let the engine overheat like that. With a water pump code present. if the coolant hits 105 ℃—which is lower than the threshold for overheat warning lights, so you won't even have seen a warning yet—it just shuts the engine right off, without even telling the power management control ECU why. The power management control ECU then sets its own P0A0F code—"hey, how come the engine's not running?"—and lights the triangle light. Of course your go pedal isn't going to get you much of anywhere then, 'cause there's no engine to do the work, and the battery all on its own is barely capable of rolling you a block or two down a city street.

But if the water pump is bogging down intermittently, the ECM might be getting fooled into letting the temperature climb above that limit. That particular 105 ℃ limit is only enforced when a water pump trouble code is current, so if the code goes away (or is cleared) and hasn't been set again yet, that limit's not enforced.

 

Sounds like it is overheating with a water pump and high temperature (too high) code. It would useful to read the engine coolant temperature with the undisclosed scanner.

Water pump flow should be visible in the reservoir when warmed up.


The temperature sensor code by itself could be air in the system or a wet connector. Might try a hair dryer on the connector near the radiator hose attached to the engine.

 

Or just use the undisclosed scanner to view the temp sensor reading. If it's something close to the right temperature you expect when the engine has been off and cooled to the temperature of the surroundings, then you don't have to spend much time on the possibility it's a wiring or connection issue. It is probably also right when the engine is running and it's saying the unpumped coolant is too hot.