What does P0123 mean?
The throttle position sensor (TPS) tells the computer how far the throttle is open. On electronic throttle systems there are two TPS signals that must agree with each other and with the accelerator pedal sensors.
The signal is reading higher than the sensor can normally produce, which points at a wiring fault or a dead sensor.
Codes are a starting point. They tell you which test failed, not which part to replace. Check for other stored codes and fix those in a sensible order.
Symptoms
- Check engine light
- Reduced power or limp mode
- Hesitation or surging
- Erratic idle
- Shifting problems on automatics
Common causes
- Open sensor ground wire
- Signal wire shorted to the 5 V reference or to battery voltage
- Water in the connector
- Failed sensor
How to diagnose P0123
- Check the sensor ground first: an open ground drives the signal high.
- Unplug the sensor: if the signal still reads high, look for a short to voltage in the harness.
- If the wiring is good, replace the sensor.
- Watch TPS voltage in live data while slowly pressing the pedal (key on, engine off). It should move smoothly with no dropouts.
- Check the throttle body for carbon buildup.
How to fix it
- Clean the throttle body (then do the idle relearn if needed)
- Repair wiring
- Replace the TPS or throttle body
Estimated repair cost
Likely repairs for P0123 run from about $100 to $900, depending on the cause.
| Repair | Typical range (parts + labor) |
|---|---|
| Diagnostic fee (scan + testing) | $100 - $200 |
| Throttle position sensor | $100 - $300 |
| Electronic throttle body replacement | $300 - $900 |
These are rough US estimates for an independent shop in 2026, based on typical parts prices and standard labor times. Dealers, big trucks, luxury brands and high-cost areas often run higher. They are not quotes. Use the repair cost estimator to adjust for your vehicle.
How serious is P0123?
High severity
Limp mode can limit speed, so plan to fix it soon. Sudden loss of power in traffic is a safety risk.
P0123 FAQ
What does P0123 mean?
P0123 stands for "Throttle/Pedal Position Sensor/Switch "A" Circuit High". The throttle position sensor (TPS) tells the computer how far the throttle is open.
Can I drive with a P0123 code?
Limp mode can limit speed, so plan to fix it soon. Sudden loss of power in traffic is a safety risk.
How much does it cost to fix P0123?
It depends on the cause. The likely repairs for P0123 range from about $100 to $900 at an independent shop in the US, plus a diagnostic fee of roughly $100-$200. These are rough estimates; dealer prices and some vehicles run higher.
What is the most common cause of P0123?
The most common causes are: open sensor ground wire; signal wire shorted to the 5 V reference or to battery voltage; water in the connector.