it came on. I've owned the car for a little over a year (1999 v70xc, 205,000 miles). It seems to run fine though. Idle isn't buttery smooth....drops about and rebounds between 850 and 1100 over about 10 seconds. I seem to have lost some mpg...but that's it.

The light goes in and out on its own. Its on more than its off, but it will turn itself off every once in a while (2 days out of 7??? or so). I drove it over three hundred miles this week with no issues.

so here's my questions. is it the dreaded ETS replacement or something else? troubleshooting steps?
What's the worst that could happen if I just ignore it?

thanks