Engine light on...

[Gromet]

OK, I was working on my stereo system, and let the battery die. Got it running again (Jumped it) and now the service engine light is on.

It is on steady... ??? Tried calling OnStar, but we are having a storm and I didn't get a direct connection so they couldn't run a diagnostic. Tried a few times but took a while to connect.

Anyone have any idea? I have it in the garage now, and aom hoping that when I leave in the morning, everything is fine again, but just wondered if any of yoiu have seen this?

2003 Black - Adv/Lux Package