DTC B1B48-12: Rear Left Outer Sensor - Circuit short to battery: Action

Refer to the appropriate system wiring diagrams and check the rear bumper harness for damage. Check sensor circuit for short circuit to power. Repair or replace any wiring harness as required
Check the connector for integrity and damage, then re-connect sensor to confirm connection
Using the manufacturers approved diagnostic system clear the DTC and run the on demand self test
If the problem persists remove the suspect sensor from the bumper. Inspect the sensor connector for signs of water ingress/corrosion. Exchange the suspect sensor with another sensor within the bumper that is not reporting a fault. Clear the DTC and run the on demand self test to confirm if the fault code now appears for the new position of the suspect sensor. Renew the faulty sensor