Mirror Passenger Horizontal Switch Circuit Short To Ground
The passenger side mirror's horizontal (left-right) control switch has a short circuit to ground, meaning electrical current is flowing where it shouldn't. Think of it like a water pipe with a hole that's letting water leak out instead of flowing to its destination.
The ECU monitors the voltage signal from the passenger mirror horizontal switch circuit. When functioning normally, the switch sends variable voltage signals; a short to ground causes the voltage to drop to 0V, which the ECU detects as an abnormal condition. The module compares this against expected resistance and voltage thresholds to identify the fault.
| Parameter | Normal Range | Fault Condition |
|---|---|---|
| Switch circuit voltage | 5V or varying 0-5V depending on switch position | Sustained 0V or below 0.5V (short to ground) |
| Circuit resistance | Variable 1k-100k ohms based on switch position | Less than 50 ohms or near 0 ohms |
Code B1748 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, B1748 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.