I changed all the fluids and filters on the new 99 today. Tranny, oil, fuel, air, and even the rearend and frontend oil. I drove it out of the shop and to town to the store and when I came back out and started it up the service engine light came back on. Will a Actron scanner take the light off or the old trick pulling the ground cables off for a few minutes and put them back on take care of it.

 

Plug the actron in and see if you can read the codes. The battery trick will work to clear the codes (remember you have 2 batteries)

Do you have any symptoms or know why the light came on in the first place?