Servo Motor Potentiometer Airintake Right Circuit Short To Ground
The air intake servo motor's position sensor (potentiometer) is electrically shorted to ground, causing the ECU to receive an invalid signal. Think of it like a dimmer switch that's stuck at zero brightness because the wiring is touching metal.
The ECU monitors the potentiometer voltage from the right air intake servo motor to determine actual intake valve position. The sensor normally outputs a voltage between 0.5V and 4.5V depending on position. When shorted to ground, the voltage remains near 0V, triggering a fault.
| Parameter | Normal Range | Fault Condition |
|---|---|---|
| Potentiometer Voltage | 0.5V to 4.5V (variable with position) | Below 0.2V continuously (short to ground) |
| Signal Resistance | 500Ω to 5kΩ (variable) | Below 50Ω (short condition) |
Code B1291 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, B1291 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.