Coil-on plug capacitive sensors and passive coil-on plug diagnostic system incorporating same

A coil-on plug ignition testing apparatus, comprising:

• a capacitive sensor comprising a first region having at least one first engagement member projecting outwardly therefrom and a second region connected to the first region and configured to slide relative to the first region, the second region having at least one second engagement member projecting outwardly therefrom, at least one of the first region and the second region comprising a capacitive element, a biasing element disposed between the first region and the second region to bias the first region toward the second region and to maintain the first region and second region in a contracted state, and an electrical connector electrically connected to at least one of the first region and the second region forming the capacitive element, wherein at least one of the first region and the second region has a substantially planar base, and wherein the first region may be translated relative to the second region against a bias of the biasing element to an expanded state for securement to a coil-on plug housing, and
• a control circuit comprising a first circuit region comprising a plurality of input electrical connectors connectable to a first plurality of capacitive sensors, a second circuit region comprising a plurality of input electrical connectors connectable to a second plurality of capacitive sensors, the second circuit region provided parallel to the first circuit region, a first capacitor comprising a region of a capacitive divider provided in at least one of the first circuit region and the second circuit region, and a first potentiometer provided in series with the first circuit region and the second region for attenuation of signals input thereto.