I have this leak when it rains that is over my battery which caused my BST harness to short, thus causing my airbag light to go on. Has anyone experience this problem? Would this be covered under the warranty?
Has anything been "touched" before in the area (ie. any previous work or aftermarket installs)? I would look at the tail light assembly. Check to see if it has water in it as well as check the seal to the body. I have seen where a leak from the tail light assembly would cause the problem you are describing. However there are multiple possibilities.