Share a caseSign in
Air intakeSeverity High: diagnose before driving on

P0120Throttle/Pedal Position Sensor/Switch "A" Circuit

What it means

The ECU has detected an electrical fault in the throttle or pedal position sensor circuit: the signal is missing, stuck or outside the range the sensor can produce. The throttle or pedal position sensor measures how far the throttle (or the accelerator pedal) is open.

Symptoms

  • Limp mode with very limited power
  • Hesitation, surging or erratic idle
  • Electronic throttle warning light

Common causes

  • Open or shorted signal, 5 V reference or ground wire
  • Corroded, loose or water-filled connector
  • Failed throttle or pedal position sensor
  • Fault on the shared 5 V reference (another sensor pulling it down)

What to check first

  1. With the key on, measure the 5 V reference and the ground at the sensor connector
  2. Back-probe the signal and compare it with live data while wiggling the harness
  3. Check for other codes on the same 5 V reference (e.g. P0641, P0651)
Can I drive with P0120? Not recommended. P0120 can lead to stalling, limp mode or engine damage; diagnose it before driving further.

Generic OBD-II meaning. Manufacturer-specific meanings and checks can differ; always check the service information for the car.

How to test the parts behind P0120

Throttle and accelerator pedal position sensorsWiring, typical values, multimeter and scope tests

Cases with P0120 (0)

Share yours

No published cases with this code yet.

Colleagues asking about P0120

Ask for help

Stuck on P0120? Describe what you measured and ask the community.

P0120: questions and answers

What does P0120 mean?

P0120: Throttle/Pedal Position Sensor/Switch "A" Circuit. The ECU has detected an electrical fault in the throttle or pedal position sensor circuit: the signal is missing, stuck or outside the range the sensor can produce. The throttle or pedal position sensor measures how far the throttle (or the accelerator pedal) is open.

What are the symptoms of P0120?

Limp mode with very limited power. Hesitation, surging or erratic idle. Electronic throttle warning light.

What causes P0120?

Open or shorted signal, 5 V reference or ground wire. Corroded, loose or water-filled connector. Failed throttle or pedal position sensor. Fault on the shared 5 V reference (another sensor pulling it down).

How do you diagnose P0120?

1. With the key on, measure the 5 V reference and the ground at the sensor connector 2. Back-probe the signal and compare it with live data while wiggling the harness 3. Check for other codes on the same 5 V reference (e.g. P0641, P0651)

Can I drive with P0120?

Not recommended. P0120 can lead to stalling, limp mode or engine damage; diagnose it before driving further.