P1121 Toyota Prius - What is the point in common with P1116 electrically

Question

I have both codes P1116 and P1121. Both include a possible electrical fault and neither seems to significantly affect actual performance. In fact because of recent seasonal degradation of mpg I can't even say with confidence either has affected mpg. If these codes are in fact caused by a bad electrical connection or short, physically where do the related wirings connect close to each other or in some way that one can affect the other. We did a complete radiator fluid professional cooling fluid replacement with no change unless that was the cause of adding a second code, since originally we only had one, the P1121.

What further confuses this is the parts diagram shows at least 2 fluid temperature sensors and an insulated fluid tank with its own temperature sensor which the parts counter man says actually contains coolant rather than oil although it is mislabeled as oil on the parts blow up diagram for the 2007 Toyota Prius. The car also has 4 water pumps one of which was replaced under warranty but no evidence of any coolant leaks of radiator fluid or oil in spite of over 150,000 miles. What makes it even harder to diagnose is the problem is not constant enough to guarantee that if we make an appointment with the dealer the codes will still be active them, yet both regularly recur and the only assurance the service department gave is that it is only a performance issue up until if it starts blinking. Performance matters but not as much as some people have paid for repairs at dealers with these 2 codes without ever actually solving the problem. Just the flow control valve itself is an absurdly expensive $623 just for the part not including installation, and for unknown reasons it doesn't even seem to be available as a rebuilt part although an integrated sensor is I understand the usual failure.

Answer 1

here is the service bulletin from toyota and what has to be replaced.

if the valve (part number 16670-21010) was replaced. I would try a coolant system flush, worst case scenario the ECM might be bad.