What Does B1349 Mean?
B1349 indicates the Body Control Module (BCM) has detected a short to battery voltage in the heated rear window (backlite) relay circuit. This means the relay control circuit is receiving constant battery voltage when it should not, preventing proper relay operation. The BCM monitors this circuit and sets this code when it detects an abnormal voltage condition indicating a direct connection to battery power.
Common Causes
40%
Damaged or chafed wiring harness between BCM and heated backlite relay causing short to power
30%
Failed heated backlite relay with internal short to battery circuit
20%
Corroded or damaged relay socket/connector with crossed terminals
10%
Failed Body Control Module with internal driver circuit fault
Diagnostic Steps
1
Step 1: Perform visual inspection of heated backlite relay, socket, and wiring. Check for melted plastic, corrosion, pushed-back terminals, or signs of water intrusion in relay socket and BCM connectors
2
Step 2: Remove heated backlite relay and measure resistance between relay control circuit terminal at BCM connector (BCM disconnected) and battery positive. Reading should be infinite (open circuit); continuity indicates short to power in harness
3
Step 3: With relay removed, use multimeter to measure voltage on relay control circuit at relay socket with ignition on. Should read 0 volts; battery voltage present indicates BCM internal fault or harness short upstream
4
Step 4: Inspect wiring harness routing from BCM to relay socket for chafing points against sharp edges, pinch points near hinges, or contact with hot components. Repair or replace damaged sections
5
Step 5: Install known-good relay and clear codes. Cycle heated backlite system on/off while monitoring live data for proper relay control voltage (should toggle between ground and battery voltage)
6
Step 6: If fault returns immediately with new relay and wiring is confirmed intact, test BCM relay driver circuit output with oscilloscope for proper switching behavior or replace BCM
Estimated Repair Cost
$75 - $450
Parts + labor, varies by vehicle and location
B1349 indicates the Body Control Module (BCM) has detected a short to battery voltage in the heated rear window (backlite) relay circuit. This means the relay control circuit is receiving constant battery voltage when it should not, preventing proper relay operation. The BCM monitors this circuit an...
The most common cause of B1349 (Heated Backlite Relay Short To Battery) is: Damaged or chafed wiring harness between BCM and heated backlite relay causing short to power
Typical repair costs for B1349 range from $75 to $450, depending on the vehicle, location, and whether you do it yourself or go to a shop.
This code does not affect vehicle safety or driveability and the vehicle is safe to operate. The heated rear window may not function properly, affecting rear visibility in cold or wet conditions, so repair should be completed before winter weather for optimal safety.
Start by connecting an OBD2 scanner to read the code and any freeze frame data. Then follow the diagnostic steps specific to B1349 to identify the root cause.
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Quick Info
Category
Body
System
Body Electrical System
Difficulty
Type
Manufacturer
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