Replaced Coolant Flow Control Valve, still have CEL & P1121

It looks like the system may not have been bled completely. You can reset the cel by disconnecting the negative cable on your 12v battery. If you have an obd2 reader you can watch the engine temp closely and see if the system clears itself by driving, but you'd have to be extremely careful that you don't overheat as you are obviously aware...

 

What steps did you take to bleed the engine? Did you run the CHRS pump several times during filling? Did you bleed the radiator at the upper bleed valve? Is the coolant level in the radiator full and stable when cold? Did you measure what you drained and did you match that when filling? I wouldn't drive if you don't have a full and stable coolant condition.

 

I went to mechanics when I first got P1121 and 2nd inverter coolant pump was replaced, however it appears the pump was in the working condition. The condition of the car was the same before/after replacing the pump. I was told the error code will go away after a few months of driving, but it didn't for 3 years. After an oil change, I got P1150 as well. I didn't go back to complain, as they recommended changing air filters for over $50 which I changed not too long ago, and realized how easy it is to do it myself. So finally I decided to research, I read the inverter pump should run quietly, and I remembered at another oil change in the long past, I started to hear clicking noise (approx 3 clicks per seconds?) when the car was starting. So I decided to do bleeding of the coolant. I didn't see much of air bubbles, but I checked and squeezed all tubes where the coolant would run, and found one tube that may have been slightly twisted causing higher pressure due to the angle. As I held the tube slightly in a different angle, I could feel the coolant was flowing freely and the pump stopped making the clicking noise, and after that, both error codes were gone. Thanks for the power of internet, that I never thought I would be opening the hood get my hands dirty, and I will never do oil changes myself, but I would pay more attention after taking car for any works are done.