Abstract: An adapter that enables the testing of secondary ignition signals of vehicle engines equipped with wireless secondary ignition systems is disclosed. The adapter detects secondary ignition voltage pulses generated by such an ignition system. It includes an input port coupled to an engine ground for receiving an electrical signal comprising a secondary ignition signal; an output port; and a filter coupled between said input port and said output port, said filter passing an electrical representation of said secondary ignition signal to said output port. In a preferred embodiment, the adapter includes a preamplifier coupled between the input port and the filter to amplify the electrical signal and an amplifier coupled between the filter and the output port to amplify the secondary ignition signal. The output port preferably is coupled to an oscilloscope allowing a technician to visually inspect the secondary ignition system waveform.