Catvega...

You say after you changed the oil the light is still on, so it was on prior to changing the oil right? You're SES is throwing codes. None of which will have anything to do with changing the oil. Go to Autozone or a shop and have them pull the codes to see what it's doing. Just remember not to panic. There are a lot of codes involved here. Some a cheap fix, some not. Start with that and I'm sure these guys here will help you out.

CHeers!
Mark

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2001 4.4i Alpine White-Bone Stock
2001 Discovery II SE7 Black (A money pit)
1996 FJZ-80 Black (with some goodies)
1969 Firebird (work in progress)