check engine soon!?

[puzz269]

Here's my problem.  I changed my oil on my 99SE-L on
Saturday afternoon and then took it for a for a quick
ride around the block.  A half hour later I go out &
start her up again and the "check egine soon" light is
on.  I had this happen once before, but the light went
off the next day.  It has only about 70k miles on it
with intake, s3 cams, stromung cat-back, & HS header.
With the exception of a crack in the header weld at
"the y", the engine is in great running order.  I've
never had any problems.  Also, the engine is not
making any unusual noises and there is no drop in
performance.  Any suggestions would be greatly
appreciated.  Thanks in advance.

Jason.