Turn Signal / Hazard Switch Signal Circuit Failure
The vehicle's computer detected a broken or disconnected wire in the turn signal or hazard switch circuit, similar to a light switch that doesn't send the signal to turn the light on. This prevents the ECU from properly detecting when you're signaling a turn or activating hazards.
The ECU monitors the voltage signal from the turn signal/hazard switch to detect switch position changes (off, left turn, right turn, hazard). It expects a valid signal within a specific voltage range when the switch is activated. If the signal is absent, shorted, or out of range, the ECU logs a circuit failure.
| Parameter | Normal Range | Fault Condition |
|---|---|---|
| Switch Signal Voltage | 0-12V with proper transitions between positions | No signal, constant high/low, or erratic voltage changes |
| Signal Response Time | Immediate response to switch actuation | Delayed or missing response when switch engaged |
Code B1875 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, B1875 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.