Vehicle Speed Pulse
WARNING: This page is about a different car, the 2011 Honda CR-V and 2010 Honda CR-V. However, it is still accessible from the selected car via links, so may be relevant.
The vehicle speed pulse is sent by the PCM. The PCM receives a signal from the countershaft speed sensor, then it processes the signal and transmits it to the audio-navigation unit and other systems.
Courtesy of AMERICAN HONDA MOTOR CO., INC.