Mirror Passenger Down Circuit Short To Battery
The passenger side mirror's down control circuit is shorted directly to battery power, preventing normal operation. Think of it like a light switch stuck in the 'on' position due to a wire touching the positive terminal.
The body control module monitors voltage on the passenger mirror down circuit, expecting controlled low voltage signals during operation. When the circuit shorts directly to battery voltage (12V+), the ECU detects an abnormal high voltage condition that exceeds safe operating thresholds.
| Parameter | Normal Range | Fault Condition |
|---|---|---|
| Mirror Down Circuit Voltage | 0-5V (PWM controlled) | Sustained 12V+ detection |
| Circuit Current Draw | 0.5-2A during operation | Excessive draw or continuous high state |
Code B1788 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, B1788 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.