P0123 means Throttle/Pedal Position Sensor/Switch A Circuit High Input. The throttle position sensor A signal voltage is higher than possible, usually a short to voltage or a lost ground. It is a generic OBD-II code, so the definition is the same on any make, but the most likely cause varies by engine; confirm with a scan tool and the service information for your vehicle before buying parts.
What P0123 means
Most vehicles built in the last two decades use electronic throttle control instead of a throttle cable: the accelerator pedal carries two or three position sensors, and the throttle body has a motor and two position sensors of its own. The computer compares the redundant sensors constantly, and any disagreement triggers reduced-power mode as a safety measure. Older engines with a throttle cable control idle with a separate idle air control valve.
P0123 symptoms
- Reduced-power mode
- High or erratic idle
- Harsh shifting
Common causes of P0123
- Short to voltage
- Open ground circuit
- Failed sensor or throttle body
How to diagnose P0123
- Check the ground circuit and connector
- Check for shorts to voltage
- Watch the signal while moving the throttle
Can you drive with P0123?
Limited; repair soon.
P0123 tips
A high-input code with a good sensor often means the sensor ground is open, so check the ground circuit voltage drop as well as the reference and signal. On electronic throttle bodies the sensor is built in, so a confirmed sensor fault means a new throttle body, followed by the throttle relearn your vehicle requires. If the code appeared right after the throttle body was cleaned or unplugged, recheck that the connector latched.
Will P0123 clear itself?
If the fault stops, the computer turns off the check engine light by itself after several drive cycles without seeing it again, and the code stays in memory as history for a while. Clearing P0123 with a scan tool after a repair is fine, but if the cause is still there the code returns, sometimes within one drive. Disconnecting the battery also clears codes on most vehicles, but it erases learned fuel trims and idle settings as well.
Related codes
| Code | Meaning |
|---|---|
| P0121 | Throttle/Pedal Position Sensor/Switch A Circuit Range/Performance |
| P0122 | Throttle/Pedal Position Sensor/Switch A Circuit Low Input |
| P2135 | Throttle/Pedal Position Sensor/Switch A/B Voltage Correlation |
Guides that help
When it is more than a sensor
Throttle and idle codes are fixed at the throttle body, the pedal, a sensor or a leak. If those check out and the engine still runs poorly, a compression test separates a control problem from a worn engine; compare engines by code on our engines page.
Shipping is a flat $80.00 per order to US addresses, with 15-day free returns. Questions? Ask a parts specialist.