Circuit/System Description
WARNING: This page is about a different car, the 2011 GMC Yukon, 2011 Chevrolet Tahoe, and 2011 Cadillac Escalade. However, it is still accessible from the selected car via links, so may be relevant.
The hybrid powertrain control module monitors the state of the 4WD range signal message, if equipped, over the serial data circuits. The hybrid powertrain control module uses this message to determine motor torque required and transmission shifting, there are no external circuits involved.