Engine-Codes - Generic - B12BF

B12BF - Heated Backlight/Mirror Relay Drive Circuit Open Or Shorted To Ground

Repair Importance Level: 3/3
Repair Difficulty Level: 3/3  What is this?
Table of contents

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

How is the B12BF code repair?

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.

What is the cost to diagnose the B12BF code

Labor: 1.0

The cost to diagnose the B12BF code is 1.0 hour of labor. The auto repair labor rates vary widely across the country, and even within the same city. Most auto repairs shops charge between $75 and $150 per hour.
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Possible Symptoms

  • Engine Light ON (or Service Engine Soon Warning Light)

B12BF Meaning

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.

More Information

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Information for specific makes

  • B12BF FORD Heated Backlight/Mirror Relay Drive Circuit Open Or Shorted To Ground
  • B12BF LINCOLN Heated Backlight/Mirror Relay Drive Circuit Open Or Shorted To Ground
  • B12BF MERCURY Heated Backlight/Mirror Relay Drive Circuit Open Or Shorted To Ground

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