Autolamp Sensor Input Circuit Short To Battery
The autolamp (headlight/daytime running light) sensor is sending a signal that's shorted directly to battery voltage, like a wire touching the positive terminal. The ECU expects a variable signal but instead detects constant maximum voltage.
The ECU monitors the autolamp sensor's analog voltage signal, which should vary based on ambient light levels (typically 0-5V). When shorted to battery, the voltage remains pinned at the high end (near 12-14V), exceeding normal thresholds and indicating a circuit fault.
| Parameter | Normal Range | Fault Condition |
|---|---|---|
| Sensor Voltage | 0.5V to 4.5V (varies with light) | >11V (battery short condition) |
| Signal Rate of Change | Gradual transitions | Stuck at maximum value |
Code B1792 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, B1792 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.