B12BF Code: Meaning, Causes, and Symptoms | OBD2 Codes
B12BF – Heated Backlight/Mirror Relay Drive Circuit Open Or Shorted To Ground
B12BF Possible Symptoms
Engine Light ON (or Service Engine Soon Warning Light)
B12BF Possible Causes
Faulty Rear Window Defrost Relay,Rear Window Defrost Relay harness is open or shorted,Rear Window Defrost Relay circuit poor electrical connection,Faulty Rear Window Defrost Switch,Faulty Rear Window Defrost Grid,Faulty Heating Ventilation Air Conditioning (HVAC) Module
The Rear Window Defrost Relay receives power from the Battery Junction Box (BJB). When the rear window defrost switch is pressed to the ON position, the Heating Ventilation Air Conditioning (HVAC) Module activates the rear window defrost relay by grounding the circuit. When activated, the rear window defrost relay supplies 12 volts to the rear window defrost grid on the circuit. The rear window defrost grid is grounded through the circuit.