WARNING: This page is about a different car, the 2013 Acura MDX, 2012 Acura MDX, 2011 Acura MDX, and 2010 Acura MDX. However, it is still accessible from the selected car via links, so may be relevant.
The knock control system adjusts the ignition timing to minimize knock.
Fig 1: Identifying Knock Sensor Terminal, Piezo Element And Diaphragm