P0123Throttle/Pedal Position Sensor/Switch A Circuit High
- Generic OBD-II code · Powertrain
- Turns on the check-engine light
- Matters for the ITP
- Can trigger limp mode
- How the car detects it
- Sensor A is, in practice, throttle position sensor 1 at the throttle body; the accelerator pedal has its own codes (P2120 onwards). With a cable-operated throttle there is a single potentiometer (about 0.5 V closed to 4.5 V wide open). Electronic throttles have two sensors sharing a 5 V reference and ground, usually running in opposite directions – on GM throttle sensor 1 falls from 3–4 V at idle to below 1 V at full throttle. P0123 means the signal voltage of sensor A is above its upper limit – usually an open sensor ground, which lets the signal float up to the reference, or a signal wire shorted to 5 V or 12 V. Limits: Ford above 4.75 V (within 1 s), Saab/GM 2011 above 4.8 V for 1 s, Saab cable system above 4.96 V for 5 s. Because GM's sensor 1 runs inverted, a high signal there electrically resembles idle, not full throttle. GM sets it after one trip; electronic throttles go into limp mode.
- What you may notice
- Check engine light, on electronic throttles also wrench lamp
- Limp mode with reduced power ('Reduced Engine Power') on electronic throttles
- Raised idle or delayed throttle response
- Shift problems on automatics
- Likely causes
- LikelySensor ground (low reference) open or high-resistance
- PossibleSignal wire shorted to 5 V or 12 V
- PossibleSensor or throttle body faulty
- PossibleMoisture or corrosion in the connector
- Inspection (ITP)
- Matters for the ITP. While the check-engine light is on, the car fails the emissions check.
- Repair
- Medium · Often possible to do yourself.Typical cost: €20 – €450
- Related codes
Explanation from obdex (CC0), exactly as the app shows it. Guidance only; confirm with a workshop.