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Common codes
P0420P0300P0171P0455P0442P0128P0401P0113

P0121: Throttle position sensor performance out of range

Drive carefully. Get it checked within a week or two.

Can I drive with P0121?

Yes, but drive carefully and get it checked soon. Throttle blade movement does not correlate with driver pedal input, leading to sluggish acceleration.

What does P0121 mean?

P0121 stands for Throttle/Pedal Position Sensor/Switch 'A' Circuit Range/Performance.

Symptoms you may notice

  • Sudden 'Reduced Engine Power' warning on dashboard
  • Gas pedal feels dead or vehicle will not accelerate past 25-30 mph
  • Jerky throttle response and abrupt engine surging

How much does it cost to fix?

Repair costs for code P0121 depend on the specific underlying root cause, ranging from simple DIY checks to component replacement. The table below lists the most common causes and rough price ranges in USD:

  • Carbon accumulation around the throttle plate
    $15-$50 common
  • Dead spot in the potentiometer sensor track
    $60-$190 common
  • Loose throttle body mounting bolts
    $10-$30 possible
  • Failing electronic throttle actuator motor
    $220-$550 rare

What to do next

  1. Remove the intake duct and clean throttle body varnish with throttle cleaner.
  2. Perform an electronic throttle relearn procedure.
  3. Check sensor voltage linearity with an oscilloscope or high-speed scanner.
Last updated: October 2026

Related codes

P0120 P0122 P0123
General guidance only, not a professional diagnosis. If the check-engine light is flashing, or the car is running rough, overheating or losing power, stop driving and get help.

About this code

Code P0121 triggers when the signal from TPS sensor A does not match expected airflow tables or secondary sensor readings. Often, heavy carbon grime along the edges of the throttle butterfly creates mechanical drag, throwing the sensor off calibration. Cleaning the throttle plate and running a calibration relearn often fixes the code .