P2122

Throttle/Pedal Position Sensor/Switch D Circuit Low

Throttle / pedal position sensor Generic OBD-II Medium

What it means

P2122 sets when the PCM sees an abnormally low voltage on the "D" throttle or accelerator-pedal position sensor circuit. That signal tells the computer how far you're pressing the pedal, so a fault often forces the car into a reduced-power limp mode. The usual culprits are a failing sensor or a wiring problem — an open, a short to ground, or a corroded connector — rather than anything mechanical.

Medium

Can I keep driving? Usually drivable but the car may enter reduced-power limp mode — acceleration can be weak or unpredictable, so drive cautiously until it's fixed.

Real-world scan data

Seen in

2,058

scans in the past year

Found in

0.3%

of scans

0.6%

of scans that found faults

Appears alongside · share of P2122 scans

P2127in 66.1% of scans

P0222in 22.8% of scans

P0123in 17.5% 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 power / limp (failsafe) mode
Poor or hesitant throttle response
Possible hard starting or stumbling

Common causes

Most likely first

Faulty 'D' pedal/throttle position sensorLikely
Open or shorted sensor signal wiringCommon
Poor or corroded connection at the sensor connectorCommon
Dirty or carbon-filled throttle bore affecting the readingLess often
Faulty Engine Control Module (ECM) — least likelyLess often

How to diagnose & fix

Work through it in order

Read freeze-frame data and check for companion 'D' circuit codes.
With the key on, engine off, check the sensor connector for a steady 5-volt reference and a clean ground.
Inspect the signal wiring and connector for opens, shorts, and corrosion; a low reading often means a short to ground or a broken reference wire.
Compare the sensor's live voltage against the accelerator position as you sweep the pedal.
Replace the pedal/throttle position sensor if it reads low or erratic. Reprogram/replace the ECM only as a last resort.

FAQ

Quick answers

Is it safe to drive with P2122?+

Short trips are usually fine, but the car may limit power or respond poorly to the pedal, which can be unsafe when merging or passing. Repair it soon.

Can I just clear P2122?+

It will come back until the low-voltage fault is fixed. Clearing it also drops the car out of limp mode only temporarily.

Read & clear P2122 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