I own a 2007 Prius and the check engline light came on. The dealership traced the problem to a damaged coolant tank that's causing a valve to malfunction.
if it is a hot coolant tank and pump. Look on ebay. You can find a used one for under $400. The replacement will cost another 400- 500.
But most likely it is a 3 way coolant flow valve. It is a known problem with these cars. The retail price is $140 plus a couple of hours of labor.
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