kevin is right about the spark plugs setting this code but the part he mentions about the engine being cold or not when removing them i would not take as a precursor to just yanking them out without paying attention to how they come out even when the engine is cold. Pay close attention to how they feel when you start to pull them out. Sometimes carbon will build up around the end of the thread shank that is protruding out inside the head. Once this occurs it wont matter if the engine is hot or cold, once it starts wiping out the threads theres no way around it tearing the threads out other than pulling the head and trying to clean up the inside carbon buildup first before removing the plug(s). Cat had this issue and came up with a different spark plug that was a tad shorter.

Knowing this can happen i made it a point to keep me a 14mm spark plug helicoil kit handy just in case there was no other way. I also use antisieze compound on the threads when installing the new ones but even using that DO NOT let any get on the end of the threads, it will harden from the heat in the chamber and create the same scenario.