The design and construction of a diagnostic device requires the development of a system for the acquisition and processing of measurement data, numerous cable connections and an on-board computer. The key component of a diagnostic system was the Fujitsu FUTRO S100 on-board computer in shock and vibration-proof housing, with passive cooling and a 16 GB Compact Flash memory card. The computer was provided with a NVOX LCD 10” VGA/FVAT touch screen. The following software was used: Windows XP-2000, USB/DeviceNet interface module and a diagnostic program. The computer was connected to the I-7565USB/DeviceNet master device via the USB port. The CAN bus connected the interface module with three slave devices collecting data from sensors installed in various locations of a wheeled tractor.