P1121 - Coolant Control Valve Replacement (with pics)

Looks like I need to replace the valve again after 11 years. Didn't get the code yet but started hearing the valve noise. Would you mind sharing the eBay seller info that sold you the Denso valve?

 

The small potentiometer in the three-way valve breaks down.
You can replace it yourself by disassembling the valve. This will save you a hundred dollars.
TOCOS RVQ121 Ceramic Potentiometer 12V 502 5K with Plate PPS-GF40 360 1PC | eBay

 

Looks like parts from China, the Amazon/eBay valves all fail in about a year and are $20. This part that's $15, maybe not worthwhile unless there's a quality part that will last?

 

A three-way faucet has a motor, a worm gear, and a potentiometer that provides feedback to stop the motor when the desired rotation angle is reached. If the potentiometer tracks are worn, the incorrect resistance reading will cause the faucet motor to rotate or stop in the wrong position.

The price RVQ121 on other sites may be less than $7 or $8

 

Wow. Thank you. Really appreciate the info.
I have already ordered a “Genuine” Coolant Control Valve from eBay shortly after posting my question to Patrick. I'll cancel or return it and go this route. May even try this on my old Coolant Control Valve that I removed 14 years ago, if I can find it.

 

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That $70 delivery price makes it more expensive than the “Genuine” Coolant Control Valve that I ordered. Tariff related? Are there other alternative sources? I did a search for TOCOS RVQ121 and found your eBay link and AliExpress, which currently is not shipping to US.

 

Perhaps due to tariff wars the cost of delivery increases several times or delivery is stopped. Unfortunately, you will have to buy some analogue of a three-way valve.

 

Quick update. I wasn't able to cancel the eBay order. The Genuine CCV arrived and it wasn't genuine. It lacked the Denso markings. I complained and the eBay seller refunded my money and let me keep the CCV. I installed the free CCV and it already failed.

I'll consider getting the potentiometer now that shipping price is back down to a reasonable amount.

 

Thanks to this thread and a few others here on PriusChat, I recently completed the successful removal and replacement of the Coolant Control Valve on my 2008 Prius. I would definitely recommend to anyone doing this repair to use the genuine Toyota replacement part. Spending a few extra dollars upfront will almost certainly prevent the future headache of having to repeat the repair due to using a poor quality, faulty aftermarket replacement (which is quite common as they fail often). I bought mine online directly from Toyota and they shipped it for free to my local Toyota dealer. Cost about $130 with tax.

My Prius started making the dreaded whir-click-whir-click-whir floppy disk mechanism noise about 10 years ago. It began as infrequent and intermittent, sometimes going away for months at a time. It wasn't until the last year or so that the noise started to become a daily annoyance, often persisting through entire drives. Then maybe three months ago it finally threw the P1121 code and check engine light. Starting after that, the check engine light would sometimes go off for a while, before coming back on, and then eventually it stayed on permanently.

I'm fairly handy but from reading many of the previous posts I was absolutely dreading doing this repair. In reality, it really isn't that bad, as nothing about it is intrinsically difficult -- remove a few bolts, disconnect an electrical connector, move some hose clamps out of the way, pull off the hoses, remove and replace the valve, then put it all back together. The only thing that makes any of this difficult is the ridiculous lack of space available.

I did mine from above by unbolting the inverter and lifting it up onto a small 2x4 block as has been detailed here many times before. If not for the cramped quarters, it might have only taken an hour to replace the valve. Instead, it took me about four hours. Most of that time was spent trying to get enough leverage on the hose clamps with my tools. It took a constantly shifting combination of hose clamp pliers, needle nose pliers, vise grips, and long-reach angled pliers to finesse the clamps off the hoses (which due to Murphy's Law were all in inconvenient positions to start with). This made things quite frustrating and resulted in more than a few scraped knuckles.

If I ever needed to do this again (which I seriously hope is never), I would probably remove the driver's side headlight or consider putting the car up on ramps to be able to remove the lowest hose from the underside. Anything to gain more access.

Using pinch-off clamps from Harbor Freight combined with some 3D-printed hose plugs and valve port caps, I only lost maybe 12 ounces or so of coolant. I first added coolant back to the radiator while opening the bleed valve, then jumped the relay to run the CHRS pump and added more coolant, then put the car in diagnostic mode and ran the engine for 30 minutes with the heat on HI and the fan on the highest setting, adding still more coolant. I was relieved when I could feel the cabin heat come on and blow hotter than I could remember it being since the car was new. I exited diagnostic mode and powered up the car normally and could see that the check engine light had turned off. At that point I called it a day.

After that, I checked the level at the radiator every morning for nearly two weeks, surprised that each morning I would typically need to top off an ounce or so of coolant that seemed to have been lost overnight. But since I could see no leaks, I knew it was just replacing air that was working its way to the top.

Finally, yesterday, I no longer needed to top off the radiator, and could see the reservoir level was holding and knew the job was done.

What a total PITA, but I'm quite happy to have saved the $1,200 I was quoted.

EDIT: One thing I forgot to mention. The night before I did the repair, I sprayed some Liquid Wrench on the bolt and the stud/nut that secure the valve to the car and let it soak in. This made it a lot easier to loosen and remove them without rounding off the bolt or snapping off the stud while removing the nut, as some others have done.