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 MICU controls the key interlock solenoid based on inputs from each switch.
Input
Output
MICU
Ignition switch (ACC) Transmission range switch (P) Park pin switch