A diagnostic apparatus for the simultaneous analysis of both positive and negative voltages as well as electrical pulses within an engine management system, said diagnostic apparatus including; a main housing box to which therein is an enclosed electronic circuitry which two or more individual indicator lights communicate from and are externally viewable by a user from said housing box, said circuitry connected to positive and negative terminals of a power supply, said electronic circuitry also connect to a first probe and a second probe, such that when a rubber boot from the back of an injector plug of an engine under analysis is removed, the pulling away of the boot from the back of the injector exposes at least two wires emerging from the back to the injector plug, such that when the engine is started, the first probe is placed upon one of the exposed wires of the injector plug thereby illuminating one of the indicator lights from the circuitry of the main housing box, and the second probe is placed upon another exposed wire at the back of the injector plug thereby illuminated another Indicator light, such that once the first probe and second probe have been placed upon. each one of the corresponding exposed wires of the injector plug, the circuitry of the main housing provides that one indicator light continually intermittently illuminates indicating a pulsating pulse whereas a continuous illumination representation of the other light confirms a constant voltage from the engine under analysis.