Door Modules
WARNING: This page does not describe the selected car, but rather 8 other vehicles, including the 2010 GMC Yukon XL, 2010 GMC Yukon, 2010 Chevrolet Tahoe, 2010 Chevrolet Suburban, and 2010 Chevrolet Avalanche. However, it is still accessible from the selected car via links, so may be relevant.
The driver and passenger door modules receive serial data messages from the side object sensors. When a message is received indicating that a vehicle or object is in the blind spot, the appropriate door module will apply voltage to the indicator located in the outside rearview mirror, illuminating the indicator. The door module provides a continuous low reference circuit for the indicator.