what is this?

[mopar3.0]

theres a box in the inner fender of my car when i take the plastic fender linner out, any ideas what it is has a a fair size plug on it too

[TheRock]

We probably need some more information. Try to take and post a picture, and be sure to tell us exactly where the box is (which side of the car), what car this is, and about how many wires are in the plug.