To be certain:
* Consult your owner's manual: This is the best resource for the precise location. A diagram would be highly helpful.
* Use a repair manual (like a Chilton's or Haynes): These manuals usually have detailed diagrams and instructions, including sensor locations.
* Search online for a diagram specific to your engine: A Google image search for "2003 Dodge Neon [2.0L or 2.4L] camshaft position sensor location" might yield helpful results.
Be cautious when searching for visual aids online, as different years and engine variations can affect sensor placement. Always double-check with your specific engine code.