P0120
Throttle/Pedal Position Sensor/Switch A Circuit
Throttle / pedal position
Generic OBD-II
High
What it means
P0120 means the ECM has detected a problem in the "A" throttle or accelerator-pedal position sensor circuit. This sensor tells the ECM how far the throttle or pedal is open, so a fault directly affects power delivery — commonly triggering reduced-power limp mode, erratic idle, hesitation, or stalling. It's worth diagnosing promptly because it affects how the vehicle responds to the pedal.
High
Can I keep driving? Drive with caution — the vehicle may drop into reduced-power (limp) mode, idle erratically, or stall; have it addressed promptly.
Common symptoms
What you'll notice
- Check-engine light on
- Reduced or limited power (limp mode)
- Hesitation, surging, or poor acceleration
- Erratic idle or stalling
Common causes
Most likely first
- Faulty throttle/pedal position sensor 'A'Likely
- Damaged, chafed, or shorted wiring in the sensor circuitCommon
- Loose or corroded connector at the sensorCommon
- Failed ECM/PCM (rare)Less often
How to diagnose & fix
Work through it in order
- Watch the throttle and pedal position values in live data while sweeping the pedal — look for dropouts, spikes, or a flat line.
- Inspect the sensor connector and harness for damage, corrosion, or loose pins.
- Check the sensor's reference voltage and ground, and test the signal voltage sweep against spec.
- Replace the throttle/pedal position sensor if the signal is faulty. Clear and re-test.
FAQ
Quick answers
Is it safe to drive with P0120?+
Only carefully. Throttle position faults often trigger limp mode or cause stalling and surging, which can be unsafe in traffic. Get it diagnosed before relying on the vehicle.
Can I just clear P0120?+
It will return quickly if the sensor or wiring is faulty, and the drivability and limp-mode issues come back with it. Fix the root cause first.
Related codes
Often seen with P0120
Read & clear P0120 yourself
Scan your car, confirm the code, and clear it once it's fixed — with OBD DashX on your phone.
✓ Verified name — SAE J2012 / ISO 15031-6Guidance reviewed by OBD DashX