I had the coolant control valve replaced in my 07 Prius but a few days later the check engine light came on andgot the same error code p1121
Welcome to PriusChat!! Who did the replacement and was all of the air properly purged? Have you check all of the fluids lately, including the radiator (under the black plastic cover) ? How are you reading the OBD2 codes? Here is the work up for P1121 : https://share.qclt.com/%E4%B8%B0%E7%94%B0%E6%99%AE%E7%91%9E%E6%96%AF%E5%8E%9F%E5%8E%82%E8%8B%B1%E6%96%87%E6%89%8B%E5%86%8Cpdf%E6%A0%BC%E5%BC%8F/Prius%20Service%20Manuals%202004/%E4%BF%AE%E7%90%86%E6%89%8B%E5%86%8C/04pruisr/05/2054m/cip1121a.pdf
A guy that has been working on my cars for a while did the replacement he has done a few of these before. Yes the fluid levels are good and I believe all of the air is purged out of the system. I had checked it with my cheap code checker and then had my mechanic check it with his professional system.
Curious which code reader you use, and how it matched up with the mechanics professional reader? How many miles, and are you the original owner? Could just be some air, but after this amount of time/miles its unlikely. Sometimes when reinstalling the vavle a hose end is swapped and secured to the wrong part of the valve. Again, not very likely. Print out the work up for 1121 (above) and have a go at it, or show it to the mechanic. It could also be the CHS tank temperature sensor, which someone else had issue with recently if I'm not mistaken. There have also been a couple of notable coolant clogs recently.
The first coolant control valve replacement failed prematurely, and you had another installed? Which manufacture, or retail source did either originate from?
