I've never seen this before. Check engine light came on and stayed on then the fuel reserve light came on and flashed quickly. I shut the key off and it went out only to return a few miles down the road. I turned the ignition off again and the reserve light tuned off quit flashing after that.
No flashing light today but the check engine light stayed on. Everything seems to be working OK and I have full power. I imagine it could any number of things but is there anything that could be quickly looked for before digging into it? It has 153K miles on it right now. How long can one expect the 02 sensor to last?

I'm pretty sure that is " Gas cap is loose / off or major evaporate system leak"

The reserve light will begin flashing as soon as the EVAP system fails the large leak test. Check to see if your gas cap is loose before you do anything else.....

Thanks, I'll have a look for that and see if I can fix it.