P0117,P261B. A cautionary tale

Thought I'd post my latest experience in case it helps anyone else avoid my mistakes.

I have a 2012 Prius C three, with 240K on her. I use it for work and can drive over 1k a week sometimes.
I started to get a check engine light and a P0117 code, Coolant Temperature sensor returning low voltage, after a 4 hr highway journey at speed, some weeks prior. I wasn't getting an overheat warning and so i cleared the code to see if it would re-occur, it didn't. I decided it may be situational but to replace that sensor anyway. Stupidly I didn't and it slipped to the back of my mind. It popped up again 2 weeks later with the overheat warning and a P261B water pump malfunction.
I limped the car home and removed the water pump. I found the expansion crack in the plastic rotor housing i expected to find and had a decision to make.
1. Get a $25 rotor for my existing pump which would take 3 days and might not fix it?
2. Get a genuine toyota water pump which the parts website was saying 3 days for pickup?
3. Go to Autozone that day and get an aftermarket water pump that looked identical and i could have that day?

I needed the car back on the road so I went with the same day option, i also got another coolant sensor as well.
After fitting the new part and refilling the coolant I was still getting P261B and an overheat warning. I burped the car more than should have been necessary but to no avail.

I ended up taking the car to the stealership and after chiding me for not using the genuine distilled-from-unicorn-blood toyota coolant, they did their own flush and refill but that didn't correct the problem. They the put on a genuine toyota pump and Viola, fixed. The aftermarket part was faulty. They also changed the thermostat as a precaution. took 2 days and cost me $1220. I was able to return the defective part to autozone and get a refund thankfully.

Moral of the story : Don't sleep on check engine codes, even if you think they are minor, and as others have said if it's a vital part always buy genuine OEM. Sometimes you can get away with aftermarket but other times it gets expensive. It's unfortunate that the genuine part wasn't available same day or I'd have fitted it and saved myself a large sum of money on labor costs.

Hope this helps others.