P0123 – Throttle/Pedal Position Sensor/Switch A Circuit High Input
What does P0123 mean?
The throttle position sensor circuit is reporting a voltage higher than the valid range — the computer is being told the throttle is open further than is physically possible, or the circuit has shorted to voltage.
What causes P0123?
Listed from most to least common:
- 1Failed throttle position sensor
- 2Short to voltage in the signal wire
- 3Open ground circuit to the sensor
- 4Damaged connector
- 5Throttle body fault on drive-by-wire systems
Code breakdown
Common symptoms
- Check engine light on
- Reduced power / limp mode
- Engine racing or surging
- Erratic idle
- Harsh or incorrect transmission shifting
How to diagnose
- 1Inspect the connector and wiring, paying attention to the ground circuit.
- 2Verify sensor ground continuity — an open ground commonly produces a high signal reading.
- 3Check for shorts to voltage in the signal wire.
- 4Sweep the throttle while watching live data for out-of-range or erratic values.
- 5Compare both throttle position signals on drive-by-wire systems.
Like P0122, this can trigger limp mode or erratic throttle behavior and should be treated as a drivability safety concern.
Common fixes and estimated costs
| Repair | Estimated cost |
|---|---|
| Repair ground or signal wiring | $100–$350 |
| Replace throttle position sensor | $120–$350 |
| Replace throttle body | $300–$900 |
Costs are rough US estimates including parts and labor. Actual pricing varies significantly by vehicle, region, and shop rates.
Good to know
An open ground circuit is a frequently missed cause of P0123. Confirm ground continuity before replacing the sensor, since a new sensor will produce the identical code if the ground is bad.
Related codes
This information is provided for general reference only and may vary by manufacturer, model, and year. It is not a substitute for professional diagnosis or repair.