Key Interlock
WARNING: This page is about a different car, the 2011 Honda Odyssey. However, it is still accessible from the selected car via links, so may be relevant.
When the ignition key is inserted into the ignition key switch, a ground signal is provided to the driver's MICU. The driver's MICU detects the insertion of the ignition key through this input. If the shift lever is out of PARK, a ground signal is provided to the driver's MICU. The driver's MICU detects that the shift lever is out of PARK through this input. The driver's MICU provides ground to the key interlock solenoid. The key interlock solenoid is then energized, which prevents the ignition key switch from being turned to LOCK (0).