[QUOTE="Godfrey, post: 144231That said, the O2 sensor triggering an indicator is still not a critical engine problem ...
That's the problem. There's no way to tell what is triggering the check engine light if it's always on. Maybe it's the 02 sensor.
Maybe there's another problem that has manifested that is also triggering it, but since it's always on, would never be addressed. That's the issue to me.
If the light was only for the 02 sensor that would be one thing (still needs to be fixed though), but it isn't. It could be for a number of things in the engine.[/QUOTE]
You said you'd been to the dealer at least once for this issue already. Didn't they check system messages?
The likelihood that the light is lit for anything else is extremely low. You worry too much.
Good luck.