Car would knock once or twice in mornings before headed to work when gas engine would turn on. I didn’t think much of it as I had no known issues or lights. After a month or so the knocking became more persistent on “cold starts”, yet no CEL. One day when gas engine turned on the engine knocked and rattled (think a diesel-like knocking) before I shut it off, afraid of what was possibly wrong. After a few minutes I cycled the vehicle back on and it ran smooth. After turning vehicle on to leave from work, the same rattle but not as bad happened - but I had a CEL. I took it into the parts store to run the Dx machine so I could possibly address the “misfire”.

The Dx machine showed a misfire in cylinder 2. I purchased the $100 coil and proceeded to swap it. After swapping the issue was still present, it was at that moment I thought something else has to be the issue. I began my intensive research to this “rattle/knock” and I was floored. There isn’t enough time to explain what all I found, but I’m sure this might point you in the right direction. Apparently the issue begins with the egr valve and egr cooler (carbon buildup).

This will lead to bigger issues which almost will testify are pricey to address. If not caught in time you will be dealing with head gasket issues and possible internal engine damage (thrown rods). Simply google (Lexus Ct200h knock or head gasket issue) and you will be overwhelmed with everyone’s issues. Lexus/Toyota has not really acknowledged this to be a known issue so they will do NOTHING to help with this issue. This issue is known to be present in the Prius world as well! Stay away from anything with this engine. I hope this saves you money and a heartache. Good luck.