What Does B1346 Mean?
This code indicates that the Body Control Module (BCM) has detected an abnormal voltage condition in the heated rear window (backlite) control circuit. Specifically, the input circuit is seeing battery voltage when it should not, suggesting a short to power somewhere in the wiring or switch circuitry. This prevents proper control of the rear window defogger system and may cause the heating elements to remain constantly powered or prevent operation entirely.
Common Causes
40%
Damaged or chafed wiring harness causing short to power between BCM and rear window defogger relay or grid
30%
Faulty heated backlite relay stuck closed or internally shorted to battery voltage
20%
Defective heated backlite switch with internal short to power circuit
10%
Failed Body Control Module with internal circuit fault on backlite control output
Diagnostic Steps
1
Step 1: Visually inspect the heated backlite relay, switch wiring, and all connectors for signs of damage, corrosion, melting, or chafing. Pay special attention to areas where harnesses pass through body panels or near sharp metal edges.
2
Step 2: With ignition off and heated backlite relay removed, use a digital multimeter to measure voltage at the BCM input circuit terminal (relay socket or connector). Reading should be 0V with switch off; if battery voltage is present, trace wiring for short to power between this point and the BCM.
3
Step 3: Test the heated backlite relay by applying battery voltage and ground to control terminals while measuring continuity across power terminals. Replace relay if it fails to switch properly or shows continuity when de-energized.
4
Step 4: Disconnect the heated backlite switch and measure resistance across switch terminals in both on and off positions. Check for unexpected continuity to power supply circuit that would indicate internal switch failure.
5
Step 5: If all external components test normal, isolate the BCM connector and measure resistance between the heated backlite input circuit pin and battery voltage pins. Infinite resistance is expected; low resistance indicates BCM internal fault requiring module replacement.
6
Step 6: After repair, clear codes, cycle the heated backlite switch on and off multiple times, and verify proper operation with no code return. Monitor live data for proper voltage signals during operation.
Estimated Repair Cost
$100 - $600
Parts + labor, varies by vehicle and location
This code indicates that the Body Control Module (BCM) has detected an abnormal voltage condition in the heated rear window (backlite) control circuit. Specifically, the input circuit is seeing battery voltage when it should not, suggesting a short to power somewhere in the wiring or switch circuitr...
The most common cause of B1346 (Heated Backlite Input Circuit Short To Battery) is: Damaged or chafed wiring harness causing short to power between BCM and rear window defogger relay or grid
Typical repair costs for B1346 range from $100 to $600, depending on the vehicle, location, and whether you do it yourself or go to a shop.
Safe to drive, but rear window defogger may not function properly, which can reduce rear visibility in cold or humid conditions. Repair when convenient, though addressing before winter weather is advisable for safety and visibility.
Start by connecting an OBD2 scanner to read the code and any freeze frame data. Then follow the diagnostic steps specific to B1346 to identify the root cause.
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Quick Info
Category
Body
System
Body Electrical System / Heated Rear Window Defogger
Difficulty
Type
Manufacturer
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