P0123 code meaning
Throttle/Pedal Position Sensor/Switch A Circuit High
Powertrain system Generic code P01xx codes Check engine light
What P0123 means
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.
P0123 at a glance
- Check engine lightYes, usually on
- Emissions testCan fail
- Limp modePossible
- Repair difficultyMedium, DIY possible
- Typical labor0.5 to 2 hours
- Clears after repairWhen cleared with a scanner
Symptoms of P0123
- 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
Common causes of P0123
- Most 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
Check the most likely causes first. Replacing parts by guesswork is the most expensive way to clear a code.
Parts involved
Throttle position sensorThrottle bodySensor wiringSensor reference voltage
What each part of P0123 means
| P | Powertrain system: engine, fuel system, ignition, emissions and transmission. |
| 0 | Generic code: it means the same on every make (SAE standard). |
| 1 | Area: fuel and air metering. |
| 23 | The exact fault in that area. |
What to do next
- Note P0123 and any other codes stored with it: several codes together often point to one cause.
- Check for loose connectors and damaged wiring around the parts the code names.
- Check open recalls for your car: some faults are fixed for free by the dealer. Enter your VIN.
- Clear the code only after the repair. If it comes back, the fault is still there.
Buying a used car? Scan it for stored codes before you pay. A recently cleared memory can hide a problem.
Questions about P0123
What does P0123 mean?
P0123 means "Throttle/Pedal Position Sensor/Switch A Circuit High". Sensor A is, in practice, throttle position sensor 1 at the throttle body; the accelerator pedal has its own codes (P2120 onwards). It is a generic code, so it means the same on every make.
Is it safe to drive with P0123?
Drive gently and only to a workshop. With P0123 the car can go into limp mode (reduced power) to protect itself.
Will P0123 fail an emissions test?
Yes, it can. P0123 is emissions-related, so most inspection programs fail a car while it is stored or while the check engine light is on.
How hard is P0123 to fix?
Difficulty: medium. A typical repair takes 0.5 to 2 hours of work. A careful DIY repair is possible with basic tools and a scanner.
Will P0123 clear itself after the repair?
Clear the code with a scanner after the repair. If the fault is fixed, it does not come back.