HELP, where to start - P0420, P1116, P1150, B1421 & B1475

You can ignore the B14xx for now, they are not pressing or relate to the Pxxxx codes.

The P1116 and P1150 do not relate to the inverter coolant pump. They have to do with the coolant heat recovery system.

The P0420 relates to the catalytic converter's efficiency. It could be related to the engine not running efficiently, or at least as efficiently as it could.

 

Techstream allows you to read freeze frame data by errors. Have you saved them?
Errors in the coolant thermos system can cause the check engine light to come on.
P1150
https://share.qclt.com/%E4%B8%B0%E7%94%B0%E6%99%AE%E7%91%9E%E6%96%AF%E5%8E%9F%E5%8E%82%E8%8B%B1%E6%96%87%E6%89%8B%E5%86%8Cpdf%E6%A0%BC%E5%BC%8F/repair%20manual/04pruisr/05/2054m/cip1150a.pdf
P1121
https://share.qclt.com/%E4%B8%B0%E7%94%B0%E6%99%AE%E7%91%9E%E6%96%AF%E5%8E%9F%E5%8E%82%E8%8B%B1%E6%96%87%E6%89%8B%E5%86%8Cpdf%E6%A0%BC%E5%BC%8F/repair%20manual/04pruisr/05/2054m/cip1121a.pdf

 

Is the catalytic converter original on the car or replaced?
P0420 requires a thorough study of the fuel-air mixture problems. It is possible that due to the old catalytic converter and engine, the burning mixture of fuel, air and oil does not turn into an environmentally friendly product at the exit of the catalytic converter.

 

touring models (years?) | PriusChat

If you had those lights going on and off while driving the first thing I would do is verify I have oil in the engine.
The only time that I know of that the check engine light will flash is for a very bad misfire.
Once a code comes in, the CEL should stay lit, not go on and off, so that's pretty unusual. Although I've never experienced it, I have read that low oil level will cause warning light flashes as oil pressure fluctuates, especially if going around a curve.