I had the same code P261B: Coolant Pump “B” Control Malfunction. I replaced the water pump, there were a couple of youtube videos that helped me with the process. You might as well do a coolant flush. I ordered the part from amazon at a better price than your local auto parts store.

It was not that hard, I just had trouble with one of bottom-side long bolts, since you don’t have much space to work with.

The part: https://www.amazon.com/gp/product/B00DUR65LI/ref=as_li_tl?ie=UTF8&camp=1789&creative=9325&creativeASIN=B00DUR65LI&linkCode=as2&tag=saneenterpris-20&linkId=eb897e6328f5a928d51360f828f16f38

The videos:

https://m.youtube.com/watch?v=Px9_LERz9Vc

https://m.youtube.com/watch?v=kLCTqzOerKg

https://m.youtube.com/watch?v=uiVy9XWW5K4

Coolant Flush:

https://m.youtube.com/watch?v=_lWLMJ_4G24

Glad to hear that you got it resolved quickly and not too expensively!

I also wanted to put it out there that you can often find parts sold by the oem manufacturer for cheaper. For example, I put one of these pumps in at a fraction of buying an OEM part. The only (visible) difference was that the Toyota logo was ground off!