P2138
Throttle/Pedal Position Sensor "D"/"E" Voltage Correlation
The two redundant accelerator pedal position sensors disagree by more than the allowed tolerance. The ECU cannot trust either signal and switches to limp-home with very limited torque. Often appears intermittently with a worn pedal sensor before failing outright.
- Check engine light: Yes
- Emissions related: Yes
- Repair difficulty: easy
Symptoms
- Check engine light on
- Reduced throttle response, possible limp mode
- Hesitation or surging
- Idle too high or too low
Common causes
Ordered by how often each turns out to be the cause.
- Pedal position sensor worn or contaminatedCommon
- Corroded pedal connectorPossible
Parts involved
- Accelerator Pedal Sensor
- Accelerator Pedal Wiring
P2138 is a generic OBD-II code defined by SAE J2012. Exact wording and diagnostic procedure vary by manufacturer and model. Code definitions are drawn from the public-domain OBDex dataset; the workshop notes are our own.