Parallel diagnostics are designed for measuring input and output signals from the electronic fuel injection module (EFI) and other modules. Measurements can be made on running engines. The system consists of a wiring harness adapter and breakout box. The breakout box is inserted between EFI module and 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 and waveforms from all systems and actuators. Disconnecting the ECU from the breakout box allows quick and reliable check of the integrity of the wiring harness in respect to continuity, and leakage currents.