P0123 Throttle/Pedal Position Sensor/Switch A Circuit High Input

P0123 indicates a high input from throttle or pedal position sensor/switch A. The module sees a signal voltage higher than the expected range.

Code details

Generic OBD-II · P0

System: Fuel / Air
Code type: Generic (SAE / ISO controlled)
Standard: SAE J2012 / ISO 15031-6

Diagnostic boundary

A diagnostic trouble code reports that a monitored test failed. It does not prove one specific part is bad, and manufacturer logic can add vehicle-specific conditions.

Do not drive around electronic throttle warnings; a high throttle-position signal can trigger reduced-power strategy for safety.

Symptoms of P0123

Check-engine light on, sometimes with rough or uneven running.
Hesitation, surging, or a noticeable change in fuel economy.
Occasionally hard starting or a smell of unburnt fuel.

Common causes of P0123

A failing or contaminated sensor (MAF, MAP, oxygen or air-fuel sensor).
Intake or vacuum leaks, or an exhaust leak near an upstream sensor.
Wiring, connector, or fuel-delivery problems that skew the reading.

Useful checks before replacing parts

Check for short-to-voltage, open ground, poor connector contact, or a sensor signal stuck high.
Compare throttle/pedal sensor A with redundant channels and commanded throttle angle.
Inspect harness routing near the throttle body and pedal assembly for chafing or water intrusion.

Related OBD-II codes

These nearby fuel / air entries can help compare wording and pin down the fault area.