Module, Blind Spot (BSM): Operation

The Blind Spot Monitor (BSM) Radio Detection And Ranging (RADAR) smart sensors are also referred to as the Left Blind Spot Sensor (LBSS) and the Right Blind Spot Sensor (RBSS), respectively. The RBSS and LBSS are each controlled by an on-board microcontroller and control circuitry. The LBSS is a master node, while the RBSS is a slave node. The two nodes communicate with each other over the Controller Area Network (CAN) - Interior High Speed (IHS) data bus. The master node then communicates with other electronic modules in the vehicle including the Body Control Module (BCM) (also known as the Common Body Controller/CBC) over the CAN-IHS data bus. In the Powernet network architecture the BCM is also a CAN bus gateway.

When a microcontroller recognizes that the appropriate conditions exist, it will energize its own sensor to generate 24 Gigahertz radar pulses through the blind spot zone on that side of the vehicle. The sensor receives and filters the radar signals being returned from any objects detected within the zone, then transmits the appropriate data identifying the relative position and speed of identified objects to the microcontroller. The microcontroller analyzes the sensor data to determine whether any detected objects should be reported.

When it is determined that an object should be reported, the microcontroller uses electronic messaging to communicate that information over the CAN-IHS data bus. The RBSS slave node reports to the LBSS master node, and the LBSS reports for both smart sensors to the other electronic modules in the vehicle.

The LBSS sends electronic messages to the Driver Door Module (DDM) (also known as the Door Control Module/DCM - Driver) and the Passenger Door Module/PDM (also known as the DCM - Passenger). The DDM and PDM each control the BSM display on their respective door through a hard wired output. The LBSS also sends electronic request messages over the CAN-IHS data bus to the Radio Receiver Module (RRM) (also known as the radio or the head unit) to generate chime tones as an audible alert. To communicate with the Instrument Cluster (IC) (also known as the Common Instrument Cluster/CIC), the LBSS sends an electronic message to the BCM. The BCM, which is a CAN-C gateway, relays the message to the IC over the CAN-C data bus.

The LBSS sends a message to the DDM and PDM to perform a bulb test by illuminating the triangle icon in its respective left or right spot display for a few seconds each time the status of the ignition switch transitions to On. Each sensor microcontroller also continually monitors the BSM system and the sensor circuits and will store a Diagnostic Trouble Code (DTC) for any fault that is detected. Both smart sensors can communicate with a diagnostic scan tool connected to the 16-way Data Link Connector (DLC) beneath the driver side end of the instrument panel.

The hard wired circuits between the sensors may be diagnosed using conventional diagnostic tools and procedures. Refer to the appropriate wiring information. However, conventional diagnostic methods will not prove conclusive in the diagnosis of the smart sensors or the electronic controls and communication between other modules and devices that provide some features of the BSM system. The most reliable, efficient and accurate means to diagnose the smart sensors or the electronic controls and communication related to LBSS or RBSS operation requires the use of a diagnostic scan tool.