Mirror Driver Down Circuit Open
The circuit that controls the driver's side mirror moving downward has lost its electrical connection, like a broken wire in a lamp cord. The ECU detected an open circuit instead of the expected electrical resistance when commanding the mirror down.
The ECU sends a command voltage to the mirror motor circuit and monitors the return current flow. It expects a specific resistance range when the down switch is activated. If the circuit is open, no current flows and the ECU detects infinite resistance or no voltage drop, triggering the fault.
| Parameter | Normal Range | Fault Condition |
|---|---|---|
| Mirror Down Circuit Current | 0.5-3.0 amps when activated | 0 amps or open circuit detected |
| Circuit Voltage Drop | Less than 1.0 volt across motor | Battery voltage present with no current flow |
Code B1779 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, B1779 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.