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.
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.
Related codes
Often seen with P2122
Read & clear P2122 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