ComboSim 1000 (J1939 & J1979 Simulator) is a small, lightweight, OBD bench simulator for OBD hardware and software development and testing. It supports both SAE J1939 and SAE J1979. The features include fixed and adjustable PGN, Diagnostic Trouble Codes (DTC) etc. The J1939 simulator is a valuable tool for the development and testing of diagnostic programs and hardware. The DTC button can be used to generate trouble codes.some of SAE J1939 compliant DMs are implemented. Physical connection is made through a standard SAE J1962 connector.