Pedal Position Not Available
The engine control unit can't read the accelerator pedal position sensor, like a car that can't tell how hard you're pressing the gas. This prevents the engine from responding properly to your throttle inputs.
The ECU monitors voltage signals from the accelerator pedal position sensor(s) to determine throttle demand. It expects a smooth linear voltage increase as the pedal is pressed, typically 0.5V at idle to 4.5V at full throttle. If the signal is missing, erratic, or outside expected ranges, the ECU cannot calculate proper fuel injection and ignition timing.
| Parameter | Normal Range | Fault Condition |
|---|---|---|
| Pedal Position Voltage | 0.5V to 4.5V (linear progression) | No signal, <0.2V, >4.8V, or non-responsive |
| Sensor Implausibility | Primary and secondary sensors match within tolerance | Primary and secondary sensor signals disagree or timeout |
Code P1581 is a moderate fault. You can generally drive to a workshop, but avoid long trips or high-load driving (motorway, uphill towing) until it is diagnosed. If the code keeps returning after clearing, or if you notice the symptoms listed above worsening, do not delay professional diagnosis. Many moderate codes have multiple possible root causes — a mechanic with live OBD data can identify the exact fault more efficiently than part-by-part trial and error.
Once the fault is repaired, P1581 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.