P0122: Throttle/Pedal Position Sensor/Switch "A" Circuit Low

P0122 means Throttle/Pedal Position Sensor/Switch "A" Circuit Low. The throttle position sensor (sensor "A") reports how far the throttle is open. On electronic throttle (drive-by-wire) systems, two or more sensors cross-check each other. The signal voltage is lower than the minimum the module expects. Typical causes are a short to ground, an open in the reference or signal wire, or a failed sensor.

CodeP0122
SystemThrottle control
SeverityHigh
TypeGeneric powertrain

Can I keep driving? Limit driving and diagnose promptly. Continued driving can cause damage, stalling or limp mode.

Common symptoms

  • Check engine light and possibly the electronic throttle warning light
  • Reduced power / limp mode
  • Hesitation, surging or erratic idle
  • Stalling
  • Poor shift quality on automatic transmissions

Possible causes

  • Failed throttle position sensor or throttle body
  • Damaged connector, often from water or heat
  • Wiring fault in the 5 V reference, ground or signal
  • Accelerator pedal position sensor fault (on drive-by-wire)

How to diagnose P0122

  1. Check the sensor reading while slowly opening the throttle: it should rise smoothly with no dropouts.
  2. On drive-by-wire, compare both sensor signals.
  3. Check the connector and the 5 V reference.
  4. After throttle body work, perform the manufacturer's throttle relearn procedure.

What the code means, digit by digit

PPowertrain0Generic (SAE) code1Sub-system22Specific fault

Generic codes have the same definition on every OBD-II vehicle (petrol cars from model year 1996 in the US, 2001 in the EU; diesels later). Manufacturers can add their own enhanced codes; those are not listed here.

Related codes

General guidance only. Fault codes describe what the engine computer saw, not which part failed: confirm with testing before replacing parts, and follow the vehicle's service information.