Turn Signal / Hazard Power Feed Circuit Short To Battery
The turn signal or hazard light power circuit is shorted directly to battery voltage, causing it to receive too much electrical power. This is like a water hose that's been punctured and spraying water everywhere instead of flowing through the nozzle.
The ECU monitors the voltage and current draw on the turn signal/hazard power feed circuit. It detects when voltage rises to battery level (12-14V) when the circuit should be de-energized or at a lower controlled voltage. The control module compares actual circuit voltage against expected operating parameters.
| Parameter | Normal Range | Fault Condition |
|---|---|---|
| Circuit Voltage (de-energized state) | 0-1V or ground | 10-14V (battery voltage present when not commanded) |
| Circuit Current Draw | 0-2A (when off) | >5A sustained (short to battery) |
Code B1872 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, B1872 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.