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 the various threads 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 needing to repeat the repair due to a poor quality, faulty aftermarket replacement (which fail often). I bought mine online directly from Toyota and they shipped it for free to my local dealership. 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 the check engine light. The CEL would sometimes turn off for a while, but eventually it stayed on permanently.

I'm fairly handy but based on previous posts I was dreading doing this repair. The process itself is pretty straightforward -- 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 the car 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, the whole thing might have only taken an hour. Instead, it took me about four hours. Most of that time was spent trying to get enough leverage on the hose clamps to move them out of the way. It took a constantly shifting combination of hose clamp pliers, needle nose pliers, vise grips, and long-reach angled pliers to work the clamps off the hoses, which due to Murphy's Law were all in inconvenient positions.

In hindsight I probably should have removed the driver's side headlight or put the car up on ramps to be able to reach the bottom hose from the underside -- anything to gain more access.

Overall it wasn't too much of a mess; I only lost about 8 ounces of coolant. I used pinch-off clamps in addition to some 3D printed plugs and caps I made for the hoses and valve ports which really helped.

To replace the coolant that was lost, I first added fresh coolant back to the radiator with the bleed valve open. Next I jumped the relay to run the CHRS pump and added a little more coolant, then put the car in diagnostic mode and ran the engine for about 30 minutes with the heat on HI and the fan on the highest setting, still adding small amounts of coolant. After that, 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.

For the next several days, I checked the level at the radiator every morning, and each morning I found it necessary to replace a small amount of coolant that had disappeared overnight from the filler neck.

Finally, as of yesterday, I no longer needed to top off the radiator, and could see the reservoir level was holding steady after several long drives, so I knew the job was done. Total hassle, but I'm quite happy to have saved the $1,200 I was quoted. Even better -- no more noise!

EDIT: Also wanted to mention, the night before the repair, I sprayed some penetrating lubricant on the bolt and the stud/nut that secure the valve to the car and let it soak in overnight. 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.