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P2121 - Throttle/Pedal Position Sensor/Switch 'D' Circuit Range/Performance

Possible causes
- Faulty Accelerator Pedal Position (APP) Sensor
- Accelerator Pedal Position (APP) Sensor harness is open or shorted
- Accelerator Pedal Position (APP) Sensor circuit poor electrical connection
- Faulty Powertrain Control Module (PCM)
Possible symptoms
- Engine Light ON (or Service Engine Soon Warning Light)
- No throttle pedal response
P2121 Description

The Accelerator Pedal Position (APP) sensor is an input to the Powertrain Control Module (PCM) and used to determine the amount of torque requested by the operator. There are 2 pedal position signals in the sensor. Both signals, APP and APP2, have a positive slope (increasing angle, increasing voltage), but are offset and increase at different rates. The 2 pedal position signals make sure the PCM receives a correct input even if 1 signal has a concern. The PCM determines if a signal is incorrect by calculating where it should be, inferred from the other signals. If a concern is present with one of the circuits the other input is used. There are 2 reference voltage circuits, 2 signal return circuits, and 2 signal circuits (a total of 6 circuits and pins) between the PCM and the APP sensor assembly. The pedal position signal is converted to pedal travel degrees (rotary angle) by the PCM. The software converts these degrees to counts, which is the input to the torque based strategy. The APP sensor fault flag is set for sensor 1 by the PCM, indicating the signal is out of the normal self-test operating range.

P2121 Information for specific makes
P2121 DODGE Throttle/Pedal Pos Sens E Minimum Stop Perf
P2121 FORD Throttle/Pedal Position Sensor/Switch 'D' Circuit Range/Performance
P2121 LINCOLN Throttle/Pedal Position Sensor/Switch 'D' Circuit Range/Performance
P2121 MERCURY Throttle/Pedal Position Sensor/Switch 'D' Circuit Range/Performance
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