What Does B2348 Mean?
This diagnostic trouble code indicates that the Body Control Module (BCM) has detected an abnormal voltage condition in the reference voltage supply circuit that powers the mirror switch assembly. The BCM monitors the positive supply voltage feeding the mirror control switch and has identified that the voltage is either too high, too low, or absent from the expected range. This fault prevents the BCM from properly receiving mirror adjustment commands from the driver.
Common Causes
40%
Open circuit or high resistance in the reference voltage supply wire between BCM and mirror switch due to corroded connectors, damaged wiring, or poor ground connection
30%
Failed or internally shorted mirror switch assembly causing voltage drop or short to ground in the reference circuit
20%
Blown fuse or faulty power distribution to the mirror switch circuit from the BCM or fuse box
10%
Body Control Module internal fault in the voltage regulator or output driver circuit supplying the mirror switch
Diagnostic Steps
1
Step 1: Perform visual inspection of the mirror switch connector and BCM connectors for corrosion, bent pins, water intrusion, or loose connections. Check mirror switch circuit fuse condition and verify continuity.
2
Step 2: Using a digital multimeter, backprobe the mirror switch connector with key on and measure the reference voltage supply pin (typically 5V or 12V depending on manufacturer). Compare reading to factory specification in wiring diagram.
3
Step 3: If voltage is absent or low at the switch connector, disconnect the mirror switch and recheck voltage. If voltage returns to specification, the switch is internally shorted and must be replaced. If voltage remains incorrect, proceed to Step 4.
4
Step 4: Perform voltage drop test on the supply wire from BCM to mirror switch connector with circuit loaded. Check for less than 0.1V drop. Inspect wiring harness for chafing, pinching, or damage along the routing path, especially at hinges and flex points.
5
Step 5: If wiring and voltage supply are confirmed good, test mirror switch operation with a scanner capable of bidirectional controls or substitute a known-good switch. Monitor BCM data stream for proper voltage feedback during testing.
6
Step 6: If all previous tests pass but code persists, suspect BCM internal fault. Verify all BCM ground connections are clean and tight, then consider BCM replacement or reprogramming if available through manufacturer service procedures.
Estimated Repair Cost
$100 - $650
Parts + labor, varies by vehicle and location
This diagnostic trouble code indicates that the Body Control Module (BCM) has detected an abnormal voltage condition in the reference voltage supply circuit that powers the mirror switch assembly. The BCM monitors the positive supply voltage feeding the mirror control switch and has identified that ...
The most common cause of B2348 (Mirror Switch Reference Voltage Positive Common Supply Voltage Fault) is: Open circuit or high resistance in the reference voltage supply wire between BCM and mirror switch due to corroded connectors, damaged wiring, or poor ground connection
Typical repair costs for B2348 range from $100 to $650, depending on the vehicle, location, and whether you do it yourself or go to a shop.
Safe to continue driving as this affects only the power mirror adjustment functionality and does not impact vehicle operation or safety systems. Repair at convenience, though proper mirror adjustment is important for safe lane changes and backing maneuvers.
Start by connecting an OBD2 scanner to read the code and any freeze frame data. Then follow the diagnostic steps specific to B2348 to identify the root cause.
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Quick Info
Category
Body
System
Body Control and Comfort Systems
Difficulty
Type
Generic (SAE)
Recommended Tools
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