P2164: Throttle/Pedal Position Sensor B Maximum Stop Performance
What to do
Check under the pedal before you book anything. A floor mat that has slid forward, a spare mat on top of the fitted one, or a bottle rolled underneath will stop the pedal reaching its full-travel stop and set this code — the car is fine, and the fix is free. If the pedal is clear, this is a sensor or a stop that has drifted rather than something broken, so ask for the relearn procedure to be tried before any part is quoted.
What this code means
The learned fully open position for sensor B no longer matches what the module expects. This is the other end of the travel from the minimum stop codes at P2109 and P2113, and the two ends fail for genuinely different reasons — which is the useful part.
Why a maximum stop is learned at all. The module does not read a pedal or a throttle in degrees; it reads a voltage, and it turns that voltage into a percentage by scaling it between two learned references — the closed stop and the open stop. Every position in between is derived from those two numbers. Move either one and the whole scale moves with it, which is why a reference drifting matters far more than the small voltage change involved would suggest.
The two ends drift differently. The closed end drifts because carbon accumulates where the plate nearly touches its bore, so the resting position creeps open year by year — that argument is set out under P2109 and it is why cleaning and a relearn fixes it. Carbon does not build where the plate is wide open, so a maximum stop code is rarely a cleaning job. What moves this end is the sensor's own output drifting after millions of cycles, a worn or fouled mechanical stop, or something physically preventing full travel.
That last one is worth checking before anything is measured, and it is free. On the pedal side the commonest obstruction is a floor mat that has crept forward, a bottle or a phone that has rolled under the pedal, or a second mat laid on top of the fitted one. The pedal genuinely cannot reach its stop, the module notices, and there is nothing wrong with the car at all. Look before you pay anyone.
What the driver feels, when there is anything to feel, is a top end that has gone missing: the engine will not deliver full power however hard the pedal is pressed, because the module has scaled full throttle to a reference that is no longer where it thinks. Many cases produce no complaint at all and only the lamp.
Likely causes
Start here
Less common
- Worn accelerator pedal assembly · moderate
- Corroded or loose connector · easy
- Faulty throttle body · moderate
Symptoms
Components involved
Information, not instruction
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Have anything you intend to act on checked by a trained person against the manufacturer's own procedure for your vehicle. Nothing here replaces that procedure.
Community experience
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