What Does B2318 Mean?
This code indicates the Body Control Module (BCM) has detected an abnormal voltage condition in the passenger side mirror vertical adjustment feedback potentiometer circuit. Specifically, the signal wire is shorted to battery voltage (12V+), causing the BCM to receive a constant high voltage reading instead of the variable resistance signal that indicates mirror position. This prevents proper vertical adjustment and position feedback for the passenger side mirror.
Common Causes
45%
Damaged or chafed wiring harness in door jamb area causing short to power wire
30%
Failed mirror motor assembly with internal short to battery voltage
15%
Corroded or moisture-damaged mirror connector causing cross-circuit short
10%
Failed body control module with internal circuit fault
Diagnostic Steps
1
Step 1: Visually inspect the door jamb wiring harness for chafing, damage, or pinching where wires flex between door and body. Check mirror connector at door for corrosion, water intrusion, or damaged pins.
2
Step 2: Disconnect the passenger mirror electrical connector. Using a multimeter, measure voltage on the vertical feedback potentiometer signal wire at the vehicle harness side - should read 0V with ignition on. If battery voltage is present, the short is in the vehicle harness between BCM and connector.
3
Step 3: If no voltage found at connector, reconnect mirror and backprobe the vertical feedback potentiometer signal wire at the mirror connector with ignition on - if battery voltage is present, the short is internal to the mirror assembly.
4
Step 4: Check resistance between the feedback potentiometer signal wire and ground with mirror disconnected - should read between 500-5000 ohms typically. Infinite resistance or 0 ohms indicates potentiometer failure.
5
Step 5: If all mirror-side circuits test normal, inspect BCM connector for corrosion or bent pins, and check for TSBs related to BCM failures. Verify proper ground connections at BCM and door ground points.
6
Step 6: After repair, clear codes, cycle mirror through full range of vertical motion multiple times, and verify proper operation and that code does not return.
Estimated Repair Cost
$150 - $650
Parts + labor, varies by vehicle and location
This code indicates the Body Control Module (BCM) has detected an abnormal voltage condition in the passenger side mirror vertical adjustment feedback potentiometer circuit. Specifically, the signal wire is shorted to battery voltage (12V+), causing the BCM to receive a constant high voltage reading...
The most common cause of B2318 (Mirror Passenger Vertical Feedback Potentiometer Circuit Short to Battery) is: Damaged or chafed wiring harness in door jamb area causing short to power wire
Typical repair costs for B2318 range from $150 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 passenger mirror adjustment functionality. Repair at convenience, though proper mirror adjustment is important for safe lane changes and parking visibility.
Start by connecting an OBD2 scanner to read the code and any freeze frame data. Then follow the diagnostic steps specific to B2318 to identify the root cause.
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Quick Info
Category
Body
System
Body Control and Accessories
Difficulty
Type
Generic (SAE)
Recommended Tools
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