Front Wiper Motor Relay Circuit Short to Vbatt
The wiper motor relay is receiving too much electrical power directly from the battery, like a switch stuck in the 'on' position. This causes an electrical short that prevents the relay from controlling the wipers properly.
The ECU monitors the wiper relay control circuit voltage through a dedicated input. It expects the relay to switch between ground and battery voltage in a controlled manner. When the circuit shorts directly to battery voltage instead of being controlled by the relay driver, the ECU detects an abnormal voltage level that remains stuck at Vbatt.
| Parameter | Normal Range | Fault Condition |
|---|---|---|
| Wiper Relay Control Voltage | 0-5V (switched between ground and Vbatt) | Stuck at 12-14V (continuous Vbatt) |
| Relay Coil Current Draw | 0.5-2A (controlled pulses) | >2A continuous (short to battery) |
Code B2107 is a low-severity fault. Your vehicle is generally safe to drive to a workshop for diagnosis. However, do not ignore it indefinitely — low-severity codes often indicate developing problems that become expensive if neglected. Book a diagnostic appointment within 2–4 weeks. If you notice any additional symptoms (rough running, power loss, unusual smells), treat it as higher priority.
Once the fault is repaired, B2107 can be cleared using any OBD-II scanner. Connect the scanner, navigate to "Clear Codes" or "Erase DTCs," and confirm. The check engine light turns off immediately.
The code will return if the root cause was not actually fixed. The ECM re-detects the fault within 1–3 drive cycles and sets the code again.