Pedal Forward / Rearward Potentiometer Feedback Circuit Failure
Your vehicle's pedal position sensor isn't sending reliable signals back to the engine computer, like a broken volume knob that won't consistently report how loud the radio is. The system detects the wiring or sensor is faulty and can't properly read forward/rearward pedal movement.
The ECM monitors the potentiometer voltage signal from the pedal position sensor as it moves forward and backward. It expects a smooth, linear voltage change within a specific range as the pedal travels its full stroke. If the signal is absent, intermittent, out of range, or doesn't correlate with pedal movement, the ECM logs this fault.
| Parameter | Normal Range | Fault Condition |
|---|---|---|
| Potentiometer Output Voltage | 0.5V to 4.5V (linear sweep) | Below 0.5V, above 4.5V, or erratic jumping |
| Signal Rate of Change | Smooth, predictable voltage transitions | Abrupt spikes, dropouts, or no signal |
Code B1990 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, B1990 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.