Abstract: A diagnostic system for a vehicle includes: a portable wireless handheld diagnostic device which is capable of sending data through wireless mode and receiving data through wireless mode; a vehicle communication interface (VCI) which interfaces between the portable wireless handheld diagnostic device and the vehicle for communicating parameters of the vehicle to the portable wireless handheld diagnostic device; and a coupler including a first port which connects to the vehicle through an in-vehicle network and a second port which connects to the vehicle communication interface (VCI). The VCI includes a vehicle data-collection and transmission component that supports communication software which collects diagnostic data from a vehicle electronic control unit (ECU) and transmits data to the vehicle ECU. The vehicle communication interface (VCI) device includes a separate internal storage device preloaded with a micro kernel which is capable of executing specific subroutines in a standalone manner.