An active region and an isolation region are formed in the surface of a silicon semiconductor substrate having a crystal plane as a principal surface. Further, the voltage conversion circuit converts a resistance value in accordance with a temperature of the head substrate into an output voltage, the relay substrate inputs the output voltage into the main-body controller, and the main-body controller detects the temperature based on the output voltage and determines the drive voltage based on the detected temperature. Consequently, regardless of the decrease of the exhaust gas recirculation quantity caused by the implementation of a large quantity of purge, the appropriate advance corrections of the MBT ignition timing and the knock limit ignition timing become possible. The detent assembly further includes a camshaft defining an aperture along the longitudinal axis to present an inner wall of the camshaft that circumscribes the longitudinal axis.