20. The method of claim 16 , further comprising the step of retrieving diagnostic information relating to said onboard vehicle control network from said database in response to a request received from said portable handheld wireless diagnostic unit after being entered via said manual input interface.
20. The method of claim 16 , further comprising the step of retrieving diagnostic information relating to said onboard vehicle control network from said database in response to a request received from said portable handheld wireless diagnostic unit after being entered via said manual input interface. 21. The method of claim 20 , wherein said information relating to said onboard vehicle control network comprises graphical information relating to said onboard vehicle control network, and further comprising the step of displaying said graphical information on a screen display at said portable handheld wireless diagnostic unit.