Probably under vehicle along frame rail -- follow fuel line from tank
there is no Chrysler neon but the Chrysler pt cruisers have the neon engine Well considering I have a 2000 Chrysler Neon i'd say the above answer is not as correct
open the driver side door, near the hinges there is a plastic piece with what looks like a slot in it, pull it out theres your box.
21 city/28 highway
It is under the housing where the lower radiator hose hooks to the engine.