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DTC codes / BMW codes / P1221

P1221 · BMWPedal Position Sensor 2 Range Performance Problem

P1221 on a BMW means the engine control module has detected that the second pedal position sensor inside the accelerator pedal assembly is not tracking the first sensor correctly or is outside its expected voltage range. The computer compares the two redundant signals and flags a performance fault when sensor 2 fails the plausibility check.

SystemPowertrain
Code typeBMW specific
SeverityMedium
Fix difficultyIntermediate
AreaFuel and air metering (injector circuits)

Symptoms you may notice

  • The check engine light or electronic throttle warning light illuminates on the dashboard.
  • The engine may enter limp mode with reduced power and a maximum engine speed limit.
  • The accelerator pedal may feel unresponsive or require more travel to accelerate.
  • Intermittent hesitation or a sudden drop in power while driving.
  • Often no symptoms besides the warning light, especially if the fault is intermittent.

Common causes, most likely first

  1. Worn or dirty tracks inside the accelerator pedal position sensor assembly.
  2. Corroded or loose electrical connector pins at the pedal sensor or engine control module.
  3. Chafed or broken wiring in the pedal sensor harness.
  4. Internal failure of the accelerator pedal module electronics.
  5. Poor ground connection shared by the pedal sensor circuit.
  6. Engine control module software or adaptation values that need resetting after a repair.

How to diagnose and fix it

  1. Read and record all stored fault codes and freeze-frame data with a BMW-capable scan tool.
  2. Inspect the accelerator pedal connector and harness for corrosion, loose pins, or chafing.
  3. Back-probe the sensor 2 signal and ground wires and compare live voltage readings against sensor 1 through the full pedal sweep.
  4. Check the sensor reference voltage and ground circuit integrity with a multimeter under load.
  5. If wiring and connectors are good, replace the accelerator pedal assembly with the integrated sensors.
  6. Clear adaptations and perform a throttle pedal relearn procedure with the scan tool.
  7. Road test the vehicle through several ignition cycles to confirm the code does not return.

Why pedal sensor 2 fails before sensor 1

  • Sensor 2 often uses a different voltage curve than sensor 1, so a fault can set even when the pedal feels normal to the driver.
  • A weak or shared ground on the pedal circuit can skew sensor 2 readings and mimic a failed pedal assembly.
  • After replacing the pedal assembly, failing to clear adaptations or perform the relearn can leave the code stored and the throttle response poor.
  • Water intrusion or spilled drinks around the pedal area commonly corrode the connector before the sensor itself fails.
  • The code can be set by a momentary voltage glitch during low battery cranking, so check battery health before condemning parts.

Can I keep driving with P1221?

You can usually drive to a workshop, but expect reduced engine power and avoid heavy acceleration or highway merging until the fault is repaired. If the pedal becomes unresponsive or the engine repeatedly drops into limp mode, stop driving and arrange a tow.

Tools that help

Tools we recommend are in the Auto Veteran shop on Amazon. As an Amazon Associate we earn from qualifying purchases.

Guidance is general and written for BMW vehicles. Exact tests and values vary by model, so confirm the fault before replacing parts.

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