Servo Motor Potentiometer Foot Circuit Open
The servo motor that controls the accelerator pedal position has an open circuit in its potentiometer feedback wire, like a broken connection preventing the engine computer from reading the pedal's actual position. The ECU can't verify the pedal sensor is working, so it triggers a fault code.
The ECU monitors the potentiometer voltage signal from the servo motor feedback circuit to confirm the accelerator pedal position matches the driver's input. When the circuit opens, the voltage signal disappears entirely, causing the ECU to detect a loss of signal and set a fault code. The module expects a continuous variable voltage within a specific range.
| Parameter | Normal Range | Fault Condition |
|---|---|---|
| Potentiometer Voltage | 0.5V to 4.5V (variable with pedal position) | Below 0.2V or above 5V (open circuit = no signal) |
| Signal Continuity | Continuous valid signal present | Signal absent or intermittent |
Code B1277 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, B1277 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.