What Does B1348 Mean?
This code indicates the Body Control Module (BCM) has detected an open circuit in the heated rear window (backlite) relay control circuit. The BCM commands the relay to energize the rear window defogger heating grid, but the module is detecting no continuity or an incomplete electrical path in the relay coil circuit or control side. This prevents the rear window defroster from functioning properly.
Common Causes
40%
Faulty heated backlite relay with open internal coil winding or corroded terminals
30%
Open circuit in wiring harness between BCM and heated backlite relay (broken wire, corroded connector)
20%
Blown fuse in heated backlite relay control circuit
10%
Failed Body Control Module with faulty relay driver circuit
Diagnostic Steps
1
Step 1: Visually inspect the heated backlite relay (typically in power distribution center/fuse box) for physical damage, corrosion, or loose connections. Check all related fuses with a test light or multimeter for continuity.
2
Step 2: Remove the heated backlite relay and test relay coil resistance with a multimeter (typically 70-120 ohms). Apply 12V directly to relay coil terminals to verify clicking and proper operation. Replace relay if faulty or coil shows infinite resistance.
3
Step 3: With relay removed, use a multimeter to check for battery voltage at the relay socket power supply terminal (key on). Verify ground circuit continuity at relay ground terminal (should read less than 1 ohm to chassis ground).
4
Step 4: Backprobe the BCM connector at the relay control wire terminal with a multimeter. Command the heated backlite on with scan tool bidirectional controls and verify BCM is providing ground signal (switching from 12V to ground). If no switching occurs, suspect BCM failure.
5
Step 5: Inspect wiring harness between BCM and relay socket for chafing, breaks, or corrosion. Perform continuity test on control wire from BCM connector to relay socket with harness disconnected at both ends.
6
Step 6: After repairs, clear codes, cycle the heated backlite switch on/off several times, and verify proper operation. Monitor scan tool data to confirm BCM shows relay commanded and activated status matches.
Estimated Repair Cost
$75 - $450
Parts + labor, varies by vehicle and location
This code indicates the Body Control Module (BCM) has detected an open circuit in the heated rear window (backlite) relay control circuit. The BCM commands the relay to energize the rear window defogger heating grid, but the module is detecting no continuity or an incomplete electrical path in the r...
The most common cause of B1348 (Heated Backlite Relay Circuit Open) is: Faulty heated backlite relay with open internal coil winding or corroded terminals
Typical repair costs for B1348 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. The rear window defroster will not function, which may reduce rear visibility during cold or wet weather conditions. Repair at convenience unless operating in conditions requiring rear defrost for safe visibility.
Start by connecting an OBD2 scanner to read the code and any freeze frame data. Then follow the diagnostic steps specific to B1348 to identify the root cause.
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Quick Info
Category
Body
System
Body Electrical System
Difficulty
Type
Manufacturer
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