A vehicle control system communication method, including: receiving, at an in-vehicle unit (IVU), a command message from a hand-held unit (HHU), wherein the command message includes a first command frame and a second command frame; and sending, from the IVU, a response message to the HHU, wherein the response message includes a first response frame, wherein the first response frame is sent in a time period between the reception of the first command frame and the reception of the second command frame.