Blind Spot Monitor System: Operation: Notes

WARNING: This page is about a different car, the 2019 Fiat 500X. However, it is still accessible from the selected car via links, so may be relevant.

The primary components of the 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. Each ECU operates on battery current received from a fuse in the Body Control Module (BCM) whenever the status of the ignition is ON and the 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. Each of these ECU communicate with each other as well as with other electronic modules in the vehicle over the Controller Area Network (CAN) data bus network.

The BSM system ECU continually monitors all of the BSM system circuits and components for readiness, and will store a Diagnostic Trouble Code (DTC) for any fault that is detected. The ECU also communicate with a diagnostic scan tool over the CAN data bus. When a BSM system ECU stores a DTC, it sends an electronic request message to the Electronic Vehicle Information Center (EVIC) in the Instrument Panel Cluster (IPC) and a SERVICE BLIND SPOT SYSTEM or BLIND SPOT SYSTEM TEMPORARILY UNAVAILABLE textual message is displayed by the EVIC to alert the vehicle operator.

The BSM system ECU also monitors electronic messages received over the CAN data bus from the Radio Receiver Module (RRM) indicating the Setup Menu settings selected by the customer for the BSM system. The BSM system ECU receive and analyze data inputs directly from the radar sensors, calculate and provide the proper hard wired outputs to illuminate the visual alert displays in their respective right or left outside rear view mirrors, as well as calculate and communicate the proper audible alert output requests to the IPC over the CAN 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 IPC based upon electronic audible alert request messages received from the BSM system ECU. The BSM system ECU also send electronic radio mute request messages over the CAN data bus to the RRM whenever an audible alert is requested. This message activates the radio mute function while the audible alert is being sounded, then resumes normal radio function when the alert is completed.

The hard wired 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, proper wire and connector repair procedures, details of wire harness routing and retention, connector pin out information and location views for the various wire harness connectors, splices and grounds.

However, conventional diagnostic methods will not prove conclusive in the diagnosis of the BSM system or the electronic controls and communication between 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.