Method and system of vehicle diagnostics based on known communication architecture of the vehicle

A handheld automotive diagnostic device configured for diagnosing a vehicle based on communication signals on the vehicle, the handheld automotive diagnostic device comprising:

• a memory circuit having computer executable instructions stored thereon, which when executed, cause the diagnostic device to:
• transmit an ECU status request signal to the vehicle;
• receive a status response signal from the vehicle, the status response signal including a plurality of ECUs on the vehicle responsive to the transmitted ECU status request signal;
• generate a state of health report including a comprehensive listing of all ECUs associated with the vehicle, each ECU in the state of health report responsive to the requested ECU status signal being associated with an active status, the remaining ECUs in the state of health report being associated with an inactive status;
• receive communication DTCs from the vehicle, each communication DTC being generated by one of the plurality of ECUs associated with an active status and each communication DTC also being associated with a possible problematic ECU;
• and
• identify a primary probable cause ECU as being one of the ECUs associated with an inactive status and also one of the possible problematic ECUs.

A vehicle diagnostic method based on an analysis of communication signals on a vehicle having a plurality of electronic control units (ECUs), the vehicle diagnostic method comprising the steps of:

• transmitting an ECU status request signal to the vehicle;
• receiving a status response signal from the vehicle, the status response signal including a first group of ECUs on the vehicle that have responded to the transmitted ECU status request signal;
• receiving communication DTCs from the vehicle, the communication DTCs being associated with a second group of ECUs;
• and
• identifying a primary probable cause ECU by comparing the second group of ECUs to the first group of ECUs, the primary probable cause ECU being included in the second group of ECUs and not in the first group of ECUs.