2010 Buick LaCrosse CEL on but fading

The check engine light came on and stayed on, doesn’t seem to have as much strength as it had before.

So have you HAD the engine checked?? And if not, why not? That light is there to tell you something is wrong. The light means there are stored error codes that can help pinpoint the problem. Take it into your trusted local independent auto repair shop soon. If it starts flashing, pull over, stop and have it towed to the show.