Wiper Brake/Run Relay Circuit Failure
The wiper motor's brake and run relay isn't communicating properly with the engine computer, like a light switch that won't send a signal back to confirm it's working. This prevents the wipers from operating or stopping correctly.
The ECU monitors the relay's feedback signal voltage when the wiper control is activated. It expects a specific voltage change when the relay engages to power or brake the wiper motor. If the relay doesn't respond or provide feedback within the expected timeframe, a fault is detected.
| Parameter | Normal Range | Fault Condition |
|---|---|---|
| Relay Feedback Voltage | 5V signal present when relay activated | No voltage change or <0.5V detected |
| Relay Response Time | 50-200 milliseconds | >500ms or no response |
Code B1431 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, B1431 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.