P1121 :(

As some may recall, our '05 has been logging an intermittent "p1121" DTC since the water pump was replaced. There are a number of threads here and elsewhere that suggest this may be due to incomplete purging of the air from the system after an engine coolant drain/refill event. After driving the car for a few thousand miles with no change in coolant level, I felt secure that the valve was bad and that there was no residual air in the system.

I ordered a new Coolant Control Valve p/n: 16670-21010 and installed it, while photo-documenting the major steps of the process. A few notes on this and I am sure Patrick or others have already posted these elsewhere...
1) The car NEEDS to be elevated at the front to remove the splash shield for access to the lower hose and clamp
2) Make SURE the car cannot be turned on, like move the keys a few hundred feet away to keep the HSD system de-energized
3) You *may* be able to get the valve out the top, I could not, so plan on it going out from the bottom
4) This is an EASY DIY job, but you MUST correctly bleed the engine coolant system afterwards (see instructions elsewhere on PC, Changing engine coolant | Page 2 | PriusChat)
5) You will need THREE coolant hose pinch-off pliers, two will not get the job done. Alternatively, perform this repair in concert with either some other coolant draining repair or during coolant replacement, then no clamps are required
6) Trapped air CANNOT cause failure of this valve, photos show how it's made and the coolant paths thru it. From that, it is obvious that DEBRIS or an electrical issue are the primary failure modes.

I documented various phases of this process, albeit poorly on YouTube here: https://www.youtube.com/my_videos?o=U

Control Valve Guts: https://www.youtube.com/edit?o=U&video_id=VOKLLRW3Jc8

Control Valve - What's under the cover: https://www.youtube.com/edit?o=U&video_id=DMrEPIQAtjg

Initial steps for removal: https://www.youtube.com/edit?o=U&video_id=YtNb9xEz8TE


Port Identification - old valve with cover off:



Disconnect items - Top View. Note: I suggest you remove the NUT from the top as the LAST thing before you remove the valve, this will prevent the valve flopping about as you work.



In this photo of the control body, we can see the scarring from debris. The valve motor would not turn at all, in either direction, with 12v applied. That explains DTC P1121