My daughter has a 2008 Prius (2nd Gen ?) with 103,000 miles. We got the P1121 code for coolant control valve. Had it replaced and all was fine for a week. Code reappeared. Mechanic said unit was bad and replaced it again. 2 weeks later code is back. Any thoughts/suggestions would be greatly appreciated. Otherwise car runs great. Thanks
Is the mechanic using OEM parts from Toyota? Does your heater work? The mechanic should check the coolant level to make sure there's enough coolant in the system.
The engine coolant loop is a somewhat tedious fill and bleed in the Gen 2 Prius. If the mechanic does not have prior Prius experience, there's a good chance the loop isn't full to capacity or fully bled. This 2 part instructional video pretty much nails it:
