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Common codes
P0420P0300P0171P0455P0442P0128P0401P0113

P0120: Throttle position sensor circuit malfunction

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

Can I drive with P0120?

Yes, but drive carefully and get it checked soon. The engine cannot accurately measure throttle pedal position, causing hesitation and limp-home mode.

What does P0120 mean?

P0120 stands for Throttle/Pedal Position Sensor/Switch 'A' Circuit Malfunction.

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 P0120 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:

  • Worn carbon tracks inside throttle position sensor
    $60-$180 common
  • Corroded throttle body wiring connector
    $30-$80 possible
  • Faulty electronic throttle body assembly
    $200-$500 possible
  • Chafed wiring harness
    $50-$130 rare

What to do next

  1. Inspect the throttle body connector for bent or backed-out pins.
  2. Sweep the throttle pedal with key on, engine off while graphing TPS voltage on a scanner.
  3. Clean carbon varnish from the throttle plate and bore.
Last updated: October 2026

Related codes

P0121 P0122 P0123 P2135
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 P0120 points to a circuit failure in throttle position sensor A. Because modern cars utilize drive-by-wire throttles, any discrepancy prompts safety protocols: the computer may illuminate an Electronic Throttle Control warning light and limit vehicle speed to 30 mph. Drive directly to a repair shop if limp mode is active.