P0123 — Throttle/Pedal Position Sensor A Circuit High
Moderate severityWhat it means
P0123 is stored when the engine control unit sees a fault involving throttle/pedal position sensor A. Throttle/pedal position sensor A tells the control unit how far the throttle or accelerator pedal is opened; it is central to drive-by-wire throttle control. A “high” reading means the signal is pinned near the top of its range — often an open circuit, a lost ground, or a short to voltage.
Common symptoms
- The live reading sits abnormally high or maxed out
- Hesitation, surging or poor throttle response
- Reduced power or limp mode
- Unstable idle
Likely causes
- Open signal or ground wire
- Signal wire shorted to a voltage supply
- Worn throttle position sensor or throttle body
- Connector or wiring fault
What to check first
- Check for an open circuit or missing ground at the sensor connector
- Watch the throttle/pedal percentage sweep smoothly from 0 to 100% in live data
- Inspect the connector and check whether a throttle relearn is needed
Can you keep driving?
Drive-by-wire faults often trigger reduced-power mode; diagnose promptly because throttle response can be unpredictable.
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