P2109: Throttle/Pedal Position Sensor A Minimum Stop Performance
What to do
Often a cheap fix. Ask for the throttle body to be cleaned and the throttle relearn procedure carried out before any part is quoted — the position is learned, and carbon slowly moves it out of range. Also worth knowing: if the throttle body was cleaned recently and this code appeared afterwards, the relearn was probably skipped.
What this code means
The learned closed position of throttle or pedal sensor A no longer matches what the module expects. This looks like an obscure code and is one of the more useful ones in the range, because it usually has a cheap answer.
What the minimum stop is. The throttle plate cannot close completely — it rests against a mechanical stop that leaves it very slightly open, which is what lets the engine idle if the motor loses power. The module learns exactly where that stop sits, because the position matters to a fraction of a degree: everything the throttle does is measured from it.
Why it drifts. Carbon builds around the plate, so the plate comes to rest a little further open each year than it did when the value was learned. Eventually the learned figure and the real one differ enough for the module to notice. The throttle body is not broken and the sensor is not broken — the reference has moved.
Which makes the repair cheap when it is caught here. Clean the throttle body and run the relearn procedure, and the reference is correct again. Skipping the relearn after cleaning is a common way to produce this code deliberately: the plate now closes further than the module expects, which is the same disagreement in the other direction.
This is the same shape as the clutch adaptation under P0810 and the gearbox actuator calibration under P0909 — an adaptive system reporting that reality has drifted past what it can absorb, rather than a part having failed.
Likely causes
Start here
Less common
- Faulty throttle position sensor · moderate
- Weak throttle return spring · moderate
- Faulty accelerator pedal position sensor · easy
Symptoms
Components involved
Information, not instruction
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Community experience
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