Start by checking the "Possible Causes" listed above. Visually inspect the related wiring harness and connectors. Check for damaged components and look for broken, bent, pushed out, or corroded connector's pins.
The cost to diagnose the B12BF code is 1.0 hour of labor. The auto repair's diagnosis time and labor rates vary by location, vehicle's make and model, and even your engine type. Most auto repair shops charge between $75 and $150 per hour.
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.
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