ASCD Steering Switch
WARNING: This page is about a different car, the 2011 Nissan Quest. However, it is still accessible from the selected car via links, so may be relevant.
ASCD steering switch has variant values of electrical resistance for each button. ECM reads voltage variation of switch, and determines which button is operated.
Refer to "AUTOMATIC SPEED CONTROL DEVICE (ASCD) : SYSTEM DESCRIPTION " for the ASCD function.