BSM not available means that the Blind Spot Monitor system is turned off or unavailable. There are several reasons why this may be the case:
-The BSM system may have been turned off manually by the driver. This can be done by pressing and holding the BSM button, typically located on the steering wheel or dash, for 3 seconds.
-If the vehicle's engine is turned off, the BSM system will also be deactivated.
-Certain driving conditions, such as heavy rain or snow, can interfere with the radar sensors used by the BSM system and cause it to become unavailable.
-If there are objects blocking the radar sensors, such as a large trailer being towed, the BSM system may become unavailable.
-Some vehicle models have a feature that automatically turns off the BSM system when reverse gear is engaged. This is to prevent false alerts when backing up into tight spaces.