Powertrain, generic (extended)

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

Check engine lightOn
EmissionsRelevant
Drive cycleNot required
Limp modePossible

P2121 means pedal signal D is electrically intact but implausible. Ford's 2012 OBD summary sets it only on second-generation ETC systems, whose pedals carry three tracks D, E and F: if sensor D disagrees with the others by more than 1.1 degrees, the PCM stores P2121 without MIL but with the wrench lamp, and pedal response becomes rate-limited using the healthy tracks. Mitsubishi lists P2121 for the accelerator pedal sensor on the 2022 Outlander as a one-trip code that turns the MIL on. Newer Ford and GM systems with two tracks report such disagreement as P2138 instead. Circuit faults on D are P2120 and P2122-P2124; P2126 is the same check for track E. The car stays drivable but reacts softly to the pedal.

Likely causes

Worn or dirty track D giving an offset reading
Contact resistance at the pedal connector
Shared reference or ground line shifting one signal

Symptoms

  • Wrench or engine warning lamp on
  • Softened, delayed acceleration
  • Idle may rise when the brake is not pressed

Repair estimate

DifficultyEasyDIY possible
Parts and labour€20–350
Time0.3–1.5 h

Typical range across vehicles; the real cost depends on what the testing finds.

Parts involved

accelerator pedal position sensorpedal sensor wiringecm

Related codes

P2120P2122P2123P2124P2126P2138

References: newtonnet.co.uk, static.nhtsa.gov, law.cornell.edu.