What Does B1347 Mean?
This code indicates the Body Control Module (BCM) has detected an abnormal electrical condition in the heated rear window (backlite) relay circuit. The BCM monitors the relay coil control circuit and has detected either an open circuit, short to ground, short to power, or excessive resistance that prevents proper relay operation. This prevents the heated rear window defrost system from functioning correctly.
Common Causes
35%
Faulty heated backlite relay with burned or stuck contacts or failed coil
30%
Damaged wiring or corroded connectors between BCM and heated backlite relay
20%
Blown fuse or fusible link in the heated backlite relay power supply circuit
15%
Failed BCM relay driver circuit or internal BCM fault
Diagnostic Steps
1
Step 1: Perform visual inspection of the heated backlite relay, relay socket, and associated fuses in the power distribution center. Check for signs of overheating, corrosion, or physical damage. Verify correct relay is installed and properly seated.
2
Step 2: Using a digital multimeter, check for battery voltage (typically 12-14V) at the relay power supply terminal with ignition on. Verify ground circuit continuity at relay ground terminal (should be less than 1 ohm to chassis ground).
3
Step 3: Remove the heated backlite relay and test relay coil resistance with multimeter (typically 70-90 ohms). With relay removed, use multimeter to check for BCM control signal voltage at the relay coil control terminal when heated backlite switch is activated (should pulse or show battery voltage).
4
Step 4: If control signal is present, install known-good relay and retest system. If control signal is absent, inspect wiring harness between BCM and relay socket for opens, shorts, or damaged insulation using multimeter continuity tests.
5
Step 5: Clear codes, operate heated backlite system through multiple on/off cycles, and verify repair by confirming code does not return and rear window defrost operates normally.
Estimated Repair Cost
$75 - $450
Parts + labor, varies by vehicle and location
This code indicates the Body Control Module (BCM) has detected an abnormal electrical condition in the heated rear window (backlite) relay circuit. The BCM monitors the relay coil control circuit and has detected either an open circuit, short to ground, short to power, or excessive resistance that p...
The most common cause of B1347 (Heated Backlite Relay Circuit Failure) is: Faulty heated backlite relay with burned or stuck contacts or failed coil
Typical repair costs for B1347 range from $75 to $450, depending on the vehicle, location, and whether you do it yourself or go to a shop.
Safe to continue driving as this only affects rear window defrost functionality. Repair is not urgent but should be addressed for proper visibility in cold/humid weather conditions and to prevent driver distraction from reduced rear visibility.
Start by connecting an OBD2 scanner to read the code and any freeze frame data. Then follow the diagnostic steps specific to B1347 to identify the root cause.
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Quick Info
Category
Body
System
Body Electrical System
Difficulty
Type
Manufacturer
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