Professional diagnostic tool for Harley-Davidson and buell workshops and tuning centers. Parallel diagnostics is designed for measuring input and output signals from the electronic fuel injection module (EFI) and other modules. Measurements can also be made on running engines. The system consists of a set of adapter cables and a breakout box. The breakout box is inserted between the EFI module and the motorcycle's wiring harness so that the system continues to function as normal. Monitoring points for all connector pins of the EFI module are clearly arranged on the breakout box. It is possible to measure signals an waveforms from all systems and actuators. Disconnecting from the ECU from the breakout box allows quick and reliable check of the integrity of the wiring harness in respect to continuity, and leackage currents.