Just OBD'ed my Prius and got 4 errors...

First one you can ignore. Just search for the code.

Second one, P0420, Cat converter? How many miles on it?

 

If you are in an emissions state you are going to have to replace your converter to get your light to go off for the 0420 code other than that the solar sensor doesn't have nothing to do with anything Just forget about it put a flashlight over it and it won't it won't come back but you know you can't leave a flashlight sitting over the Sun sensor. But that's all that is that has nothing to do with anything The PO420 you're going to need to converter You can also try a spacer but not a spark plug anti Fowler a solid steel stainless probably spacer with a little piece of catalytic material in the middle of it that may work but your state that has emissions may kick you out because of that spacer so you have to know what you're doing where you are

 

B1421 just means the car was in the shade. It is literally what it says. "Solar sensor" == "is the car in the sun".

 

A bright flashlight pointed at the sensor will replace sunlight.))
Just like a shadow will block sunlight during the day so that the error value appears B1421.

 

That code has nothing to do with the sensor that screwed into the pipe before or after your cat The code you have is the catalyst is below threshold not the O2 sensor is not working right? So just so you don't chase your tail or someone else's tail usually this code involves the catalytic converter internals cannot pass the flood test that the car's computer runs on the cat every so often You can change your O2 sensors to your blue in the face and spend thousands of dollars on 15 of them and when that doesn't change then you can spend the real money on a cat or whatever it is you have to do in your country in a long time since I had to do any dealings with motor vehicles in Sweden like 1963 so I don't know what you have but I'm guessing you have some form of some type of emissions or some annual semi-annual something that the car has to be looked at to keep it roadworthy especially in rust countries like Sweden and places where cars can rust away But then again maybe you don't and if you don't hats off too ya. I don't have emissions either I can have the check engine light on from now until myself or the car expires with no problems at all some places you cannot do this Good luck with your project