What Does B2347 Mean?
This code indicates that the Body Control Module (BCM) has detected a voltage on the mirror switch reference circuit that is below the expected threshold. The BCM supplies a reference voltage (typically 5V) to the mirror switch assembly to monitor switch position and commands. When this supply voltage drops below specification, the BCM sets this fault code, indicating a problem in the power supply circuit feeding the mirror switch.
Common Causes
40%
Damaged wiring harness or corroded connector between BCM and mirror switch assembly causing high resistance or short to ground
30%
Failed mirror switch assembly with internal short circuit pulling reference voltage low
20%
Faulty Body Control Module with degraded internal voltage regulator or output driver
10%
Chafed or pinched wiring creating intermittent short to ground in mirror switch circuit
Diagnostic Steps
1
Step 1: Perform visual inspection of mirror switch connector and wiring harness at driver's door jamb and under dash, checking for corrosion, damaged pins, water intrusion, or physical damage to wiring
2
Step 2: Using a digital multimeter, backprobe the mirror switch connector with ignition ON and measure reference voltage supply from BCM (should read 4.5-5.5V typically). If voltage is low with switch connected, proceed to Step 3
3
Step 3: Disconnect mirror switch assembly and re-measure reference voltage at harness connector. If voltage returns to normal specification, mirror switch has internal fault. If voltage remains low, wiring or BCM is faulty
4
Step 4: With mirror switch disconnected, measure resistance between reference voltage circuit and ground. Should read open circuit (OL). If low resistance detected, locate and repair short to ground in wiring harness
5
Step 5: If wiring tests good but voltage still low, check BCM ground circuits for high resistance (should be less than 0.5 ohms to chassis ground). Poor BCM ground can cause low reference voltages
6
Step 6: Clear codes, reconnect all components, cycle ignition, and verify repair by operating mirror switches through all positions and rescanning for codes
Estimated Repair Cost
$100 - $650
Parts + labor, varies by vehicle and location
This code indicates that the Body Control Module (BCM) has detected a voltage on the mirror switch reference circuit that is below the expected threshold. The BCM supplies a reference voltage (typically 5V) to the mirror switch assembly to monitor switch position and commands. When this supply volta...
The most common cause of B2347 (Mirror Switch Reference Voltage Positive Common Supply Low Voltage) is: Damaged wiring harness or corroded connector between BCM and mirror switch assembly causing high resistance or short to ground
Typical repair costs for B2347 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 only affects power mirror adjustment functionality. Mirrors will remain in their current position but may not be adjustable electrically. Repair at convenience, though proper mirror adjustment is important for safe lane changes and reversing.
Start by connecting an OBD2 scanner to read the code and any freeze frame data. Then follow the diagnostic steps specific to B2347 to identify the root cause.
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Quick Info
Category
Body
System
Body Control System - Mirror Control
Difficulty
Type
Generic (SAE)
Recommended Tools
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