P1121 and inside the coolant valve

You can buy that pot , i took one apart and googled the number and found the part and mount on the web. Brought up a Japanese site with all kinds of crazy ricer stuff for the prius....

SM-G960U ?

 

I mentioned on another thread linking to this, but not here, that Lisle sells a "62140 seized fastener removal master kit" that works, like, miracles with stuck screws like that.

It works with an air hammer, and it doesn't exert any twist force on the screws so doesn't break them off. It just steadily bops the screw on the head a couple thousand times a minute while you gently turn with a wrench on the tool. Screws come right out and you won't even flatten the corners of the Phillips head.

I don't work for Lisle or get any cut, but I've worked some miracles I wouldn't have been able to without it.

 

I've used the thing successfully on stuff you might not expect. That housing looked like most of the threaded inserts are located where you could back them up against something solid. And nice and easy on the air hammer trigger. It's not how hard the whacks, it's how many; if humans could swing a light hammer 2,000 times a minute, just that and a regular screwdriver would do it.

 

Does it imply the failure of these valves may not actually be caused by the mechanical part (motor, gear, valve body), but rather by the potentiometer in it?

 

Gen 2 Prii used that kind of potentiometer position sensing in lots of places, and Gen 1 in even more. Gen 2 has it in that valve (which sounds like a washing machine when the bad position signal is making it hunt for position), and in the three HVAC door servos (which sound like mice in the dash when the bad position signal is making them hunt for position), and maybe others.

Gen 1 also used the same design for the steering torque sensor (do a search for "steering gear jitters" or "wheel shakes like wet dog") and for the accelerator pedal sensor (do a search for "big hand syndrome", i.e., the pedal position gets a flaky read and it feels like a big hand has suddenly reached from the sky to slow down your car).

The mechanicals I suppose can wear out, eventually, but the potentiometer position sensing does flake out, very commonly; it's the first thing to check, and usually easy to fix.

If your valve motor or mechanism was mechanically worn out or jammed, you would probably find it stuck or not working at all. If it's making the washing-machine noise actively hunting back and forth for the right position, it's not mechanically dead.