The service engine soon light has come on.

What is your question?

I just had a new radiator and thermostat put in last week. I have had sensors replaced, new rear brake lines, alternator, battery, plus much, much more in the engine before inspection in October last year. I do know my valve cover has a small crack in it which my son will be repairing this week but the service engine light just came on today? Any ideas/suggestions on why the light may be on??? Thank you very much for your time and input.