Blind Spot Monitor System: Notes
The primary components of the Blind Spot Monitor (BSM) system are the microcontroller based Electronic Control Units (ECU) integral to each of the two Radio Detection And Ranging (RADAR) sensors, one behind each outboard side of the rear bumper fascia. The two sensors are known as the Right Blind Spot Sensor (RBSS) and the Left Blind Spot Sensor (LBSS). Each ECU operates on battery current received from a fuse in the Power Distribution Center (PDC) whenever the status of the ignition switch is ON. Each ECU has a path to ground at all times through a take out and eyelet terminal of the body wire harness that is secured to the body sheet metal. The ECU of the RBSS and the LBSS each communicate with each other or with a diagnostic scan tool over the Controller Area Network - Interior High Speed (CAN-IHS) data bus network.
However, the LBSS ECU is a master node, while the RBSS is a slave node. Only the master node can communicate directly with other electronic modules in the vehicle. Each BSM system ECU continually monitors its own BSM system circuits and components for readiness, and will store a Diagnostic Trouble Code (DTC) for any fault that is detected. When either ECU stores a DTC, it is the LBSS master node that sends an electronic request message to the Instrument Panel Cluster (IPC). The IPC will then display a SERVICE BLIND SPOT SYSTEM or BLIND SPOT SYSTEM TEMPORARILY UNAVAILABLE textual message in the Electronic Vehicle Information Center (EVIC) to alert the vehicle operator. The LBSS sends that request via the CAN-IHS bus to the Body Control Module (BCM). In the Powernet network architecture the BCM is also a CAN bus gateway and will relay messages received on the CAN-IHS data bus to the IPC over the CAN-Chassis (CAN-C) data bus.
The LBSS ECU also monitors electronic messages received over the CAN-IHS data bus from the IPC through the CAN-C bus via the BCM gateway indicating the customer programmable features settings for the BSM system. Each BSM system ECU directly controls, receives and analyzes data inputs from its own radar sensor, but when the ECU in the RBSS calculates the need for an alert it sends an electronic message over the CAN-IHS bus to the ECU of the LBSS. Then the LBSS provides the proper electronic messages over the CAN-IHS bus to the BCM as well as to the Driver Door Module (DDM) or Passenger Door Module (PDM). The DDM and PDM use hardwired outputs to illuminate the visual alert displays in their respective right or left outside rear view mirrors. The LBSS also communicates the proper audible alert output requests over the CAN-IHS data bus to the BCM gateway, which relays those requests to the Radio Receiver Module (RRM) over the CAN-C data bus.
The BSM radar sensors allow the BSM system ECU to locate and identify nearby objects of interest meeting the criteria established by algorithms within the system software. The BSM displays provide the vehicle operator with a visual alert indicating that an object of interest has been detected within one of the vehicle detection zones. The BSM audible alerts are then issued by the RRM through the appropriate audio system speakers based upon electronic audible alert request messages received from the BSM system ECU.
The hardwired circuits between components related to the BSM system may be diagnosed using conventional diagnostic tools and procedures. Refer to the appropriate wiring information. The wiring information includes wiring diagrams, details of wire harness routing and retention, connector pin-out information and location views for the various wire harness connectors, splices and grounds. For proper wire repair, and connector repair procedures. Refer to STANDARD PROCEDURE and refer to REMOVAL or INSTALLATION .
However, conventional diagnostic methods will not prove conclusive in the diagnosis of the BSM system or the electronic controls and communication between the ECU and other devices that provide some features of this system. The most reliable, efficient and accurate means to diagnose the BSM system or the ECU and communication related to BSM system operation requires the use of a diagnostic scan tool. Refer to the appropriate diagnostic information.