Side Object Sensors
WARNING: This page is about a different car, the 2009 Cadillac STS. However, it is still accessible from the selected car via links, so may be relevant.
The side object sensors are each located behind the rear fascia, positioned so that the sensor is pointing out toward the opposite lane. Each sensor is supplied B+ and ground. The right sensor receives an additional ground. Both sensors communicate independently on the serial data line. The serial data enters the right sensor in a pass-thru configuration, the connects to the left sensor. The scan tool is able to individually communicate with each sensor.
When a vehicle or object is detected by a side object sensor, a serial data message is sent to the appropriate door module to illuminate the indicator located in the outside rearview mirror.