@Idahogo, like db4690 above says, your fault code doesn't have anything to do with the accelerator pedal or electronic throttle system. It's for a coolant control valve. There is a service bulletin out for this and an updated replacement part from Toyota that is required to repair this fault. I believe the cost should be in the $300-$350 range.
Any previous work or recall you had performed related to the pedal isn't relevant here.
@db4690, I have had mixed results with an AirLift coolant vacuum fill, I rarely use it anymore. For the Prius I open all the bleeder valves, put the gas engine in service mode so it stays running and operate the water pumps to bleed the system. But yes, whoever does this work needs to be familiar with the system.