As promised, the results posted for posterity. After properly following all advice of the knowledgeable members here and checking fuel pressure, wiring, all the grounds I could find, starter cables, and following the "sticky" thread on directions for diagnosing a bad opti, I concluded the opti was bad despite the fact that it was only a couple of months old.

I must add this; for those who have a problem such as this one, it is imperative that you do everything you can to find the problem before you start throwing money at it by changing parts that it "could" be. All of the things I checked and used troubleshooting methods to eliminate cost me NOTHING except time.

Changed the opti yesterday. Thus far, I have no SES. Car is running like a champ, both cold and hot. I let it sit in the driveway idling yesterday for 30 minutes after refilling the coolant system, then drove 30 miles without a problem. Another 30 this morning to work, also trouble-free. If the problem resurfaces in the near future, I will repost and start over.

Thanks to all who replied and offered advice.


Clift notes, it was the opti.