What Does B2107 Mean?
This diagnostic trouble code indicates that the Body Control Module (BCM) has detected an unintended voltage supply (battery voltage) on the control circuit for the front wiper motor relay. The BCM expected to see a controlled ground or low voltage signal when commanding the relay, but instead detected constant battery voltage, suggesting a short circuit to the positive power supply. This prevents the BCM from properly controlling the wiper motor relay operation.
Common Causes
40%
Damaged or chafed wiring harness causing the relay control circuit to contact a power wire or junction
30%
Failed wiper motor relay with internal short circuit connecting control terminal to power terminal
20%
Moisture intrusion or corrosion in BCM connector causing terminal cross-contamination and voltage bleed
10%
Faulty Body Control Module with internal driver circuit failure creating false voltage detection
Diagnostic Steps
1
Step 1: Perform visual inspection of the wiper motor relay and connector for signs of burning, melting, or corrosion. Remove the relay and inspect all terminals for damage or contamination.
2
Step 2: With ignition off and relay removed, use a digital multimeter to measure voltage on the relay control terminal at the relay socket. Reading should be 0V; if battery voltage is present, trace wiring back toward BCM for short to power.
3
Step 3: Check resistance between the relay control circuit pin and known good ground with all connectors disconnected. Should read infinite resistance (open circuit); low resistance indicates a short to power somewhere in the harness.
4
Step 4: Inspect wiring harness routing from BCM to relay location, particularly areas where harness passes through firewall, near sharp metal edges, or contact points with moving components. Look for wire insulation damage or pinch points.
5
Step 5: Install a known-good relay and clear codes. Operate wipers through all switch positions while monitoring live data for voltage on relay control circuit. Voltage should cycle with BCM commands; constant battery voltage confirms wiring or BCM fault.
6
Step 6: If all wiring checks pass, check BCM connector terminals for spread pins, corrosion, or moisture. Clean and repair as needed, then retest. If problem persists with verified good wiring, BCM replacement may be required.
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 unintended voltage supply (battery voltage) on the control circuit for the front wiper motor relay. The BCM expected to see a controlled ground or low voltage signal when commanding the relay, but instead detec...
The most common cause of B2107 (Front Wiper Motor Relay Circuit Short to Vbatt) is: Damaged or chafed wiring harness causing the relay control circuit to contact a power wire or junction
Typical repair costs for B2107 range from $100 to $650, depending on the vehicle, location, and whether you do it yourself or go to a shop.
Vehicle is safe to drive in dry conditions, but inoperative or intermittently functioning wipers create a significant safety hazard in rain or snow. Repair should be completed before driving in inclement weather conditions.
Start by connecting an OBD2 scanner to read the code and any freeze frame data. Then follow the diagnostic steps specific to B2107 to identify the root cause.
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Quick Info
Category
Body
System
Windshield Wiper System
Difficulty
Type
Generic (SAE)
Recommended Tools
OBD2 Scanner
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