Wiper Front Power Circuit Failure
The power circuit supplying your front windshield wipers has failed or lost electrical connection, similar to a light switch that won't turn the light on. The vehicle's body control module detected abnormal voltage or no signal in the wiper motor circuit.
The body control module monitors voltage and current draw in the front wiper power circuit when the wipers are commanded on. It detects open circuits, short circuits, or excessive resistance that prevents normal motor operation. The BCM compares actual circuit performance against expected voltage and current parameters.
| Parameter | Normal Range | Fault Condition |
|---|---|---|
| Wiper Motor Supply Voltage | 12-14V when activated | Below 9V or open circuit |
| Motor Current Draw | 3-8 amps under load | Zero amps (open) or excessive spike (short) |
Code B1840 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, B1840 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.