Communication Enable Circuit Description
WARNING: This page is about a different car, the 2020 GMC Acadia. However, it is still accessible from the selected car via links, so may be relevant.
Devices on High Speed GMLAN Bus enable or disable communication based on the voltage level of the Serial Data Communication Enable circuit or Accessory Wakeup Serial Data circuit. When the circuit voltage is high (around 12 V), communications are enabled. When the circuit is low, communications are disabled.