981 · Engine

P0121

Throttle/Pedal Position Sensor/Switch "A" Circuit Range/Performance

HIGH SEVERITY

Throttle/pedal position sensor "A" reading is implausible.

SYMPTOMS

  • Check-engine light
  • Rough idle or hesitation
  • Reduced performance
  • Worse fuel economy

LIKELY CAUSES

  • Faulty or drifting throttle position sensor
  • Wiring/connector fault
  • Mechanical/intake condition skewing the reading
  • ECM/PCM fault (rare)

DIAGNOSIS STEPS

  • Compare throttle position sensor live data against other sensors for plausibility
  • Inspect wiring and connector
  • Check for related mechanical causes (leaks, restriction)
  • Verify reference voltage and ground
  • Replace the sensor if out of spec

RELATED PARTS

  • Throttle body (drive-by-wire)
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