I would triple check the connectors.
Could be a pin that is not correctly seated and maybe got pushed back in the shell.
I`ll add this just for the grins.
DIAGNOSIS AND TESTING - BLIND SPOT MONITOR SYSTEM
WARNING:
To avoid serious or fatal injury on vehicles equipped with airbags, disable the Supplemental Restraint System (SRS) before attempting any steering wheel, steering column, airbags, airbag curtains, knee blocker, seat belt tensioner, impact sensor or instrument panel component diagnosis or service. Disconnect the Intelligent Battery Sensor (IBS)/negative battery cable assembly from the negative battery post, then wait two minutes for the system capacitor to discharge before performing further diagnosis or service. This is the only sure way to disable the SRS. Failure to take the proper precautions could result in accidental airbag deployment.
The following textual messages related to the Blind Spot Monitor (BSM) system may appear within the Instrument Panel Cluster (IPC):
BLIND SPOT SYSTEM OFF - This message to the vehicle operator when the ignition first transitions to the ON status indicates that the BSM system has been turned off using the Setup Menu of the Radio.
SERVICE BLIND SPOT SYSTEM - This message to the vehicle operator while the ignition status is ON indicates that the BSM system is unavailable due to a monitored system fault or faults.
BLIND SPOT SYSTEM TEMPORARILY UNAVAILABLE - This message to the vehicle operator while the ignition status is ON indicates that the BSM system is temporarily unavailable as a result of one of the following:
Sensor Blockage - The amber BSM visual icon in both outside rear view mirrors will be illuminated as long as blockage exists or until the ignition status transitions to OFF, whichever occurs first.
Monitored System Fault - The BSM system has detected a monitored system fault condition and has stored a Diagnostic Trouble Code (DTC). The amber BSM visual icon will be illuminated in both outside rear view mirrors for as long as the condition exists or until the ignition status transitions to OFF, whichever occurs first.
NOTE:
If the BLIND SPOT SYSTEM TEMPORARILY UNAVAILABLE message is received for a minimum of 5 minutes, please verify that sensor enclosures on the sides of the tail lamps where the radar sensors are located is not blocked by snow, ice or road debris. If the area is blocked, remove the blockage and cycle the ignition.
NOTE:
If the vehicle has experienced any trauma in the sensor enclosures on the sides of the tail lamps where the sensors are located, even if the fascia is not damaged, the radar sensor may have become misaligned. A misaligned radar sensor will result in the BSM system not operating properly.
To calibrate the Blind Spot Sensor:
Drive the vehicle over 13 mph (20 kp/h) on a straight path for longer than one minute.
Once this criteria is met, both mirror Light Emitting Diodes (LEDs) will go from active to off and the DTC will store. The DTC can now be cleared.