P0120–P0225 Throttle/Pedal Position Sensor/Switch A Circuit
The ECU has logged a fault on P0120. The definition below is the exact wording the standard uses for this code.
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 |
|---|---|---|
P0120 | Throttle/Pedal Position Sensor/Switch A Circuit | Investigate soon |
P0220 | Throttle/Pedal Position Sensor/Switch B Circuit | Investigate soon |
P0225 | Throttle/Pedal Position Sensor/Switch C Circuit | Investigate soon |
The definition
P0120: Throttle/Pedal Position Sensor/Switch A Circuit.
P0120 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:
- Read the freeze-frame data stored with the fault - engine speed, load and temperature at the moment it logged tell you whether this happens cold, hot or under load.
- Check the connector at the part for corrosion, and that it is fully seated.
- Clear the code and see whether it returns, and under what conditions.
What actually causes this on a VAG
Every modern VAG is drive-by-wire: there is no cable from the pedal to the throttle. The pedal has its own position sender and the throttle body has its own angle sensors, and this code says one of those signals is outside what the ECU will accept. It usually comes with the EPC light and reduced power, because when the ECU cannot trust the throttle position it deliberately limits the engine. The generic description covers both ends of the system, so the first job is finding out which one your car is actually complaining about.
Most likely causes, in order
- Connector or wiring at the throttle body or pedal. Corroded or water-damaged pins, a plug not fully latched after other work, or a loom chafed where it crosses from the body to the engine. Read the fault in a VAG-aware tool rather than a generic reader - it will name the throttle drive angle sensors (G187/G188) or the accelerator pedal sender (G79/G185), which tells you which end to inspect. That distinction alone can save you buying the wrong part.
- Low sensor reference voltage or a poor earth. The throttle and pedal sensors run off the ECU's regulated supply. If that supply is being dragged down by a fault elsewhere, throttle codes appear even though the throttle is fine. Look for reference-voltage codes such as P0642 or P0643 stored alongside, and check the battery terminals and engine earth straps - a tired battery can produce a surprising spread of odd codes on these cars. This is worth ruling out before you buy any part.
- The accelerator pedal module has failed. If the fault text names the pedal sender rather than the throttle, the pedal assembly is replaced as one unit. Watch the pedal value in live data while pressing slowly all the way down - a flat spot, a jump, or a momentary dropout confirms it, and it is a far cheaper part than a throttle body.
- The throttle body has failed internally. A well-known VAG fault. The position sensors are inside the throttle valve control module and are not sold separately, so the unit is replaced complete. The usual picture is a persistent EPC light, limp mode, and a throttle angle in live data that does not track the pedal smoothly. It is the most expensive item on this list, so prove it before you buy it.
Worth knowing: Take the reduced power seriously while this is stored: the car can drop into limp mode without warning, so leave yourself room when pulling out or overtaking until it is fixed. After fitting or removing a throttle body - and sometimes after a battery disconnection - the throttle must have its basic setting or adaptation run with a diagnostic tool. Skip that step and the car can stay in limp mode with a brand new part fitted, which sends plenty of people back to the shop convinced the replacement is faulty. Also, never force the throttle flap open by hand or blast an electronic throttle body with harsh carburettor cleaner; you can wreck a working unit in seconds.
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 P0120 mean?
P0120 means Throttle/Pedal Position Sensor/Switch A Circuit. It is logged when the ECU sees this circuit outside its expected operating window.
Can I drive with P0120?
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.