P2120

Throttle/Pedal Position Sensor/Switch D Circuit

Throttle / pedal position Generic OBD-II Medium

What it means

P2120 means the engine control module sees an out-of-range signal in the 'D' throttle/accelerator-pedal position sensor circuit. On drive-by-wire vehicles the ECM relies on this sensor to know how far the pedal is pressed; when the signal is faulty it often defaults to a reduced-power limp mode to keep the car controllable.

Medium

Can I keep driving? The car usually runs but may drop into reduced-power limp mode; drive gently and get it checked soon, since throttle response can become unpredictable.

Real-world scan data

Seen in

791

scans in the past year

Found in

0.1%

of scans

0.2%

of scans that found faults

Appears alongside · share of P2120 scans

P0226in 71.3% of scans

P0225in 62.5% of scans

P0657in 47.0% of scans

Figures reflect only diagnostic scans recorded through our own apps and tools. Cars are typically scanned because a symptom or warning light prompted it, so these counts describe our scan records — not the incidence of faults in any model, and not the quality, reliability, or safety of any vehicle. No comparison between manufacturers or models is implied. All trademarks belong to their respective owners; no affiliation or endorsement is implied.

Common symptoms

What you'll notice

Check-engine light on
Reduced engine power / limp mode
Poor or erratic throttle response
Unstable idle or unexpected stalling

Common causes

Most likely first

Faulty accelerator-pedal / throttle position sensor (circuit D)Likely
Open, shorted, or chafed sensor wiringCommon
Poor or corroded connector at the sensorCommon
Dirty or carbon-filled throttle bore skewing the sensor readingLess often
Faulty ECM (rare)Less often

How to diagnose & fix

Work through it in order

Inspect the pedal/throttle position sensor connector and wiring for damage or corrosion.
With key on, engine off, confirm a steady 5-volt reference and a good ground at the sensor.
Check that the D-circuit signal sweeps smoothly as the pedal/throttle moves.
Clean the throttle bore if carbon build-up is affecting readings.
Replace the sensor if its signal is out of range; retest before condemning the ECM.

FAQ

Quick answers

Is it safe to drive with P2120?+

It's drivable, but the car may limp with reduced power and throttle response can be inconsistent. Keep speeds low and get it diagnosed promptly.

Can I just clear P2120?+

You can, but a genuine sensor or wiring fault brings it right back and can drop the car into limp mode again.

Read & clear P2120 yourself

Scan your car, confirm the code, and clear it once it's fixed — with OBD DashX on your phone.

▶ Get it on Google Play

✓ Verified name — SAE J2012 / ISO 15031-6Guidance reviewed by OBD DashX