Well, well, well, well,.....(think 'A Clockwork Orange'), well, well, well!
I have an '05 Camry that has a CEL that never shuts off. I can change the oil and a day or two later, it never fails to come right back on. A knod for consistency. I've had it for six years now without any other noteworthy issues. Dealers and others have shown me the key, switch, steering cloumn,... key, switch, steering column trick to shut it off, and, oh yes, that works,...for a little while. Maybe twenty four hours...a little tounge in cheek here please. But then it is right back on to keep me company again. It does shut off from time to time completely randomly (everybody's gotta eat I guess), but never for long.
I know this is the inverse of your problem but it is interesting to see the results of bigger companies relying on multiple vendors for the same component and it's sometimes many sub-components. Ya never know what ya gonna get. BTW, Click & Clack, my older brother and I were changing engines in my dad's side yard back in the early seventies in Burlington, MA. My dad however, grew up in Your Fair City, in East Cambridge on Spring St. back when men were men and cars needed constant attention.