In doing some research on this, I found a lot of sources which had egt ecu fault codes. This appeared to be either bad sensors or bad wiring in most cases. Most cars have egt sensors to protect the cat or turbo, and most trip around 950*C. I don't think you can install just any type K thermocouple and have it work. It must have the right mounting hardware, and the type of electrical wire and wiring junctions you use can grossly affect the accuracy of the measurement. Buy the oem part.

Not responsible for advice not taken...