Trucktester supports generic SAE J1939 diagnostics. This feature can be used to diagnose specific ECUs not supported by TruckTester, such as custom body builder modules, or completely unsupported trucks.

The generic SAE J1939 diagnostics is also known to work also on other special vehicles such as RZR XP4 900 (2013 model) off-road 4x4 vehicle.

ECUs are only numbered, ECU numbering is usually dependent on vehicle manufacturer. Usually Engine has address "00", transmission is "03", engine retarted "0F", ad-blue dosing "3D".

Only fault code reading/clearing is supported in generic J1939 mode. Suspect parameter numbers (SPNs) defined by SAE J1939 are decoded in this mode.

TruckTester allows selection of CAN-BUS speed.