16. A method for facilitating diagnosis and maintenance of one or more control networks, comprising; wirelessly communicating over a wireless channel between a wireless ground station and a wireless interface coupled to an onboard vehicle control network located on a mobile conveyance; coupling the wireless ground station to a local area computer network comprising a server computer, a database comprising diagnostic information relating to said onboard vehicle control network, and a wide area network interface, whereby additional diagnostic information relating to said onboard vehicle control network is obtainable from one or more remote computers; conveying instructions from the handheld wireless diagnostic unit to the onboard vehicle control network in response to inputs entered at a manual input interface of the handheld wireless diagnostic unit; wirelessly communicating between a portable handheld wireless diagnostic unit and said onboard vehicle control network via said wireless interface and with said local area computer network via said ground station thereby receiving the diagnostic information pertaining to the onboard vehicle control network from the local area computer network via said wireless interface, wherein said portable handheld wireless diagnostic unit is not physically connected to said onboard vehicle control network; and displaying communications received by the portable handheld wireless diagnostic unit on a graphical display of the portable handheld wireless diagnostic unit.
16. A method for facilitating diagnosis and maintenance of one or more control networks, comprising; wirelessly communicating over a wireless channel between a wireless ground station and a wireless interface coupled to an onboard vehicle control network located on a mobile conveyance; coupling the wireless ground station to a local area computer network comprising a server computer, a database comprising diagnostic information relating to said onboard vehicle control network, and a wide area network interface, whereby additional diagnostic information relating to said onboard vehicle control network is obtainable from one or more remote computers; conveying instructions from the handheld wireless diagnostic unit to the onboard vehicle control network in response to inputs entered at a manual input interface of the handheld wireless diagnostic unit; wirelessly communicating between a portable handheld wireless diagnostic unit and said onboard vehicle control network via said wireless interface and with said local area computer network via said ground station thereby receiving the diagnostic information pertaining to the onboard vehicle control network from the local area computer network via said wireless interface, wherein said portable handheld wireless diagnostic unit is not physically connected to said onboard vehicle control network; and displaying communications received by the portable handheld wireless diagnostic unit on a graphical display of the portable handheld wireless diagnostic unit. 22. The method of claim 16 wherein the wide area network comprises the Internet.