P2121: Throttle/Pedal Position Sensor/Switch D Circuit Range/Performance — what it means, the affected system and what to check before replacing parts.
Meaning, symptoms, causes and checks
Throttle/Pedal Position Sensor/Switch D Circuit Range/Performance. Basic catalogue definition; diagnostic details have not yet been reviewed.
Affected system: Powertrain
Symptoms
- Engine warning and uneven acceleration may occur.
- Some vehicles enter a reduced-power mode when pedal/throttle input is implausible.
Possible causes
- A worn or defective position sensor signal track D.
- Loose, broken or corroded wiring between the pedal/throttle sensor and controller.
- An actuator or control issue may require consideration only after circuit checks.
What to check
- Read associated codes and determine the sensor providing channel D on this vehicle.
- Inspect pedal-area and throttle connectors for corrosion, damage or loose pins.
- Graph position signals during a slow pedal sweep; note gaps or implausible readings.
- Check circuit supply, ground and continuity against manufacturer specifications before replacing the sensor.
Also written as: P2121-00, P212100 (some scan tools add the fault-type byte, e.g. -00).