P0123–P0228 Throttle/Pedal Position Sensor/Switch A Circuit High
The voltage on this circuit is sitting near battery voltage. Typically a short to a positive feed, or a disconnected sensor floating high.
Can you drive it? The engine light will stay on and the car may run in a reduced-power mode. Read the freeze-frame data to see the conditions the fault was logged under.
Which code is which
Same fault, different cylinder or bank — diagnosed the same way. Several set together usually means one shared cause.
| Code | Definition | Severity |
|---|---|---|
P0123 | Throttle/Pedal Position Sensor/Switch A Circuit High | Investigate soon |
P0223 | Throttle/Pedal Position Sensor/Switch B Circuit High | Investigate soon |
P0228 | Throttle/Pedal Position Sensor/Switch C Circuit High | Investigate soon |
The definition
P0123: Throttle/Pedal Position Sensor/Switch A Circuit High.
P0123 is a powertrain code (the engine or gearbox), defined by the SAE standard - it means the same thing on any make of car, and any generic OBD-II reader will decode it.
What to check first
Cheapest and fastest checks first:
- Unplug the sensor and check whether the signal falls. If it stays high, suspect the wiring rather than the sensor.
- Check the earth path - a missing earth makes a sensor read high.
What actually causes this on a VAG
Same sensor as P0122, opposite complaint: the ECU is seeing more voltage on the throttle position signal than is physically possible. A signal with nothing pulling it down commonly floats high, so this usually means a broken earth or an open circuit - or the signal wire touching a live feed. As with the low-voltage version the sensor lives inside the electronic throttle body, and the car will normally be sat in limp mode with the EPC light on.
Most likely causes, in order
- Broken or high-resistance sensor earth. An open or high-resistance earth makes a perfectly good sensor sit at the top of its scale, which looks identical to a dead sensor. The senders inside the throttle unit share a supply and an earth, so if both throttle position signals go implausible at the same moment - rather than one on its own - suspect that shared earth or the connector rather than believing two sensors failed at once.
- Connector or loom damage. Water ingress, corrosion, or a chafed signal wire touching a switched live all produce a stuck-high reading. Inspect both halves of the plug, then flex the loom by hand with live data on screen - the value will usually jump when you reach the damaged section.
- Failed throttle valve control module. Possible, but only after the supply, earth and signal at the plug have all been shown to be sane with the unit disconnected. Replacing it without that check is the most common way people spend a lot of money on this code for nothing.
Worth knowing: An unplugged or open-circuit sensor commonly reads high, which is exactly what this code describes - so a cracked plug or a single broken wire is a far better first bet than a failed throttle body. Fix the wiring, then re-run the throttle adaptation before spending anything. And treat an intermittent one as urgent rather than something to live with: the EPC light here comes with a power cut that can land at the worst moment.
Reading the code is the easy part
A code names the circuit that complained. What tells you why is watching the sensor behind it while the engine runs — and that is where a code reader stops and a diagnostic tool starts.
VAGPULSE reads every module in a VW, Audi, Skoda or SEAT — not just the engine — shows the live measuring blocks behind this fault, gives you the freeze-frame conditions it was logged under, and clears it once you have fixed it. It also does what a generic OBD reader cannot on a VAG: service resets, coding, adaptations, and Stage 1–3 flashing with your original file saved first.
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Common questions
What does P0123 mean?
P0123 means Throttle/Pedal Position Sensor/Switch A Circuit High. The voltage on this circuit is sitting near battery voltage. Typically a short to a positive feed, or a disconnected sensor floating high.
Can I drive with P0123?
The engine light will stay on and the car may run in a reduced-power mode. Read the freeze-frame data to see the conditions the fault was logged under.