Service Engine Soon idiot light

I rescued a 1992 Olds 98 Regency Elite from a garage where it had sat undriven for over 3 years, with only 40K miles. When I replaced the dead battery it started right up. I added fresh gasoline and fuel injector cleaner. It runs just fine. The question is this: The Service Engine Soon light comes on and sometimes goes off. Is this a false negative that will go away after a few tanks of fresh gasoline? Or is it warning that should be heeded immediately?

You can pull the diagnostic trouble codes yourself to determine what’s causing the Check Engine light to come on. Here’s a link.