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

What does P0123 mean?

The A position-sensor signal is above its calibrated range. Depending on the vehicle this input belongs to the throttle or pedal sensing system; it does not necessarily mean the driver is pressing the accelerator fully.

Generic OBD-II definition: Throttle/Pedal Position Sensor/Switch A Circuit High Input. Confirm applicability in your vehicle service information.

Common causes

• Signal shorted to voltage
• Lost sensor ground or damaged connector
• Faulty or insecure position sensor

Symptoms

• High or unstable idle
• Surging
• Reduced or unreliable throttle response

Diagnostic focus

A signal stuck high with the pedal released is an electrical or sensor-position clue. Do not adjust throttle stop screws to compensate for an invalid voltage.

Can I keep driving with P0123?

Severity: High Unreliable throttle response can be dangerous. Do not continue driving with surging, stalling, or reduced acceleration that makes traffic unsafe; arrange recovery instead. Do not force an electronic throttle plate.

If the check engine light is flashing or the car runs badly, stop driving and have it checked.

Typical fixes

• Identify sensor A and its pinout
• Test signal and ground against the service specification
• Inspect mounting and compare live position data before replacing parts

Sources & review

• OBD-Codes.com: P0123
• TroubleCodes.net: generic code definitions

Definitions and diagnostic background checked 2026-11-06. Generic guidance, not a substitute for the service procedure for your exact year, engine, and transmission.