Driver Power Window Down Circuit Short To Ground
The driver's side power window has an electrical short to ground in its down circuit, like a wire touching metal when it shouldn't. The car's computer detects abnormally high current flow and triggers this fault code.
The ECU monitors current draw through the driver window motor circuit during operation. When a short to ground occurs, current spikes dramatically above normal operating levels. The module detects this overcurrent condition and logs the fault before cutting power to the circuit.
| Parameter | Normal Range | Fault Condition |
|---|---|---|
| Window circuit current | 2-8 amps during operation | >15 amps or continuous ground connection detected |
| Circuit voltage | 12-14V when active | <2V indicating short to ground |
Code B1406 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, B1406 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.