Throttle/Pedal Position Sensor/Switch D Circuit High
What it means
P2123 means the ECM sees an abnormally high voltage on throttle/pedal position sensor circuit D — usually the accelerator pedal position sensor. Because a modern throttle is drive-by-wire, an untrusted pedal signal often triggers a reduced-power limp mode. The usual causes are a shorted signal wire, a bad ground, or a failing sensor.
Can I keep driving? Often drivable, but the car may fall into a reduced-power limp mode since the pedal signal can't be trusted.
Real-world scan data
Appears alongside · share of P2123 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, often a limp/failsafe mode
- Hesitation or poor throttle response
- Unstable idle
Common causes
Most likely first
- Faulty accelerator pedal / throttle position sensor D (signal reads too high)Likely
- Signal wire shorted to voltage or to the 5V referenceCommon
- Open in the sensor ground circuit (pushes the signal high)Common
- Poor connection or corrosion at the sensor connectorLess often
- Rarely, a faulty ECM/PCMLess often
How to diagnose & fix
Work through it in order
- Read freeze-frame data and confirm the D circuit is the one flagged.
- Inspect the pedal/throttle sensor connector and wiring for shorts to voltage, opens, and corrosion.
- Backprobe the sensor (key on, engine off): the D signal should sit in normal range, not pinned high.
- Check the sensor ground for continuity — a bad ground drives the signal high.
- If wiring and ground are good, replace the pedal/throttle position sensor and retest.
FAQ
Quick answers
Is it safe to drive with P2123?+
Can I just clear P2123?+
Related codes
Read & clear P2123 yourself
Scan your car, confirm the code, and clear it once it's fixed — with OBD DashX on your phone.