A controller area network diagnosis instrument for diagnosis and evaluation of electronic components on a vehicle control system (10). The controlled area network diagnostic instrument (CANDI) includes a computer processor (119) with a graphics display (121). The processor (119) has a cable (132) to plug into the diagnostic connector (36) engaged to a common data bus (18) of the vehicle (101). The processor (119) is programmed to graphically show a mock gauge cluster or vehicle instrument panel (120) on the display (121) in that has the same appearance as a real vehicle gauge cluster or vehicle instrument panel (102). When connected to the diagnostic connector, the processor (119) mines data off of the data bus (18) and converts it into human readable form on the display (121). This may take the form of mock conventional gauges (124), mock warning lights (105), mock switch status (123), or mock LCD displays (126) shown via computer graphics on the processor's display (121).