2010 Prius with P261B water pump failure

Try resetting the code and then disconnect the power from the 12V for 5 minutes.

Then reconnect the 12V and try and start the car.

The system shuts the car down when the coolant gets hotter than 225F

Damage will start to happen if it hotter than 214F for a long time.

 

The original mistake was in assuming too much about what "hybrid system failure" means, and in assuming one "hybrid system failure" would be the same as an earlier "hybrid system failure", and in assuming it's reasonable to keep driving because there's "only" a hybrid system failure.

The car's hybrid system consists of many important parts including the gasoline engine and the transmission—pretty much everything involved in making the car move—and has a couple hundred different ways it can fail (counting just the ways there are trouble codes for).

When you get the warning triangle and the message, the thing to do next is to read the trouble codes so that you know what type of failure is being reported. Trying to assume or guess that information is a big gamble.

There is an overheat light on the dash, but it seems to come on around 248 ℉, which you can think of as a usual threshold of "overheating" when otherwise the engine is working right.

But an engine with a water pump malfunction is not working right. Its coolant isn't even circulating, so it has hotter spots and cooler spots and expansion stresses and the temperature sensors don't show what's going on except in the stagnant coolant right where the sensors are. So having a pump malfunction is a bigger problem than any ordinary "overheat", and that's why the ECM cuts the engine at 221 ℉ if there's a pump failure.

 

I have a 2015 Prius v3.I got a check engine light on few days ago. I went to advance auto to get it checked and it gave me a code p261b(1/3) stored. Engine Coolant Pump "B" control malfunction. After doing some search and watching YouTube videos I got to know it's Water Pump. So I ordered one. It took me 2 days to receive parts. Now my check engine light is gone and car runs fine. I have driven around 30 miles to check if light comes back on or it engine gets overheated. Nothing happened.
From last 2 weeks I noticed that my car is not giving enough miles like it used to. I used to get around 49 miles/gallon and now its only around 35-36 miles/g. I do not know a lot about cars. I feel some fumes on my tongue since check engine light came on.
I just want to know if I should go ahead and change water pump or wait till CE light comes on or there is something else wrong with it.

Thanks