100k miles Check engine light (MIL) came on, dealers (3) found no TC logged ???

What is your question?

also had autozone and napa scan no TC logged. select clear codes on scanner and indicates codes erased, check engine light comes back on at end of drive cycle. It is my understanding both mechanical and electrical issues can turn on the check engine light, only electrical failure (sensor reading) will log coeds in the ecm. what mechanical areas should i look for.