P2123
Throttle/Pedal Position Sensor/Switch D Circuit High
Throttle actuator control
Generic OBD-II
Medium
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.
Medium
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.
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?+
The car may limit power for safety since it can't trust the pedal signal. Drive gently and repair it soon.
Can I just clear P2123?+
It comes back until the shorted/open circuit or failed sensor is repaired.
Related codes
Often seen with P2123
Read & clear P2123 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