What does the light look like? Try looking under the passenger seat for washer fluid (truck) or at the rear hatch (van).
You'll have to try posting a pic of the light. Someone posted the same question here 5 years ago, with no resolution as far as I can tell. Also post more details, transmission type (CVT/manual), truck/van, etc. Since it's a 1999, you might be able to get a proper code using and OBD-II code reader (Napa or AutoZone should be able to let you borrow one). I've used a Fram CA7775 air filter, but that's for a 1991 and it may not be the same as yours.