Replacing expensive parts based on guesswork seldom works out…There ARE wrecked or otherwise scrapped Prius’s available to pick parts from, but which parts? You KNOW the answer from dealership mechanics—$4000. Finding an independent mechanic who is familiar enough with the Prius to successfully repair it using used parts may be easier said than done…
People who wish to buy high-mileage high-tech cars need to educate themselves as to how to maintain and repair them. I suspect the diagnostic equipment needed to diagnose these cars is proprietary to Toyota Dealerships. So now we are back to guess-work…I would just add the four grand to the tuition bill, write it off as an educational expense…