As suggested above, I left my keys in the kitchen and went into the garage after the vehicle sat all night. As soon as I opened the back left side door I heard the clank. After following this thread, I'm thinking that it is more of a gear or actuator engaging or disengaging. I don't think that a fuel pump priming will create this type of sound. Now to be fair it is possible that the fuel pump is priming as well but it may be silent. So to me a faulty RDU seems to be the likely culprit. Especially since mine was built Feb 13 right in the middle of the build dates noted above. Will check in with the dearler.