P2102–P210C Throttle Actuator A Control Motor Circuit Low
The voltage on this circuit is sitting near zero. Typically a short to earth, or a sensor that has failed to its low end.
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 |
|---|---|---|
P2102 | Throttle Actuator A Control Motor Circuit Low | Investigate soon |
P210C | Throttle Actuator B Control Motor Circuit Low | Investigate soon |
The definition
P2102: Throttle Actuator A Control Motor Circuit Low.
P2102 is a manufacturer-specific powertrain code (the engine or gearbox). Its meaning is set by the carmaker rather than by the SAE standard, so a generic OBD-II reader will often show it as an unknown code or misread it.
What to check first
Cheapest and fastest checks first:
- Unplug the sensor. If the reading jumps to full scale, the wiring is fine and the sensor has failed low.
- Check the sensor's 5V supply and its earth before condemning the sensor itself.
What actually causes this on a VAG
This is the same drive-by-wire throttle motor as P2100 - VAG's J338 throttle valve control module - but here the ECU is seeing the motor's control circuit pulled low, towards earth, or drawing more current than it should. The result is usually the same: EPC light, the throttle held near closed and a car stuck in limp mode. Because it is a short rather than a break, the cause is more often something touching the wiring than the motor simply wearing out.
Most likely causes, in order
- Chafed wiring shorting to earth. Follow the throttle body loom from the plug back and look wherever it crosses metal - the block, a bracket, a heat shield or a cable tie that has cut in. Rubbed-through insulation with a bright witness mark on the metal behind it is the giveaway.
- Water or corrosion in the throttle body connector. Moisture bridging two pins looks exactly like a short to the ECU. Common on cars parked outside, cars with blocked scuttle drains, or after an enthusiastic engine bay wash. Open the plug, dry it, clean the pins and re-grease with proper electrical contact grease.
- Throttle motor shorted or binding internally. A worn motor, or a flap stiff with carbon, drags excessive current and can be read as a low-side fault. Separate it from the wiring with a simple test rather than a purchase: with the ignition off, unplug the throttle body, then clear the codes and let the ECU look again. If the low or short fault comes straight back with nothing connected, the problem is in the loom or the ECU. If it changes to an open-circuit code instead, the throttle unit is the suspect. Expect the test itself to add throttle-position codes - that is normal with the plug off, and they clear once it is reconnected.
- Engine ECU driver stage. Only after the loom, connector and throttle unit have been ruled out. This is uncommon and an ECU swap brings coding and immobiliser work with it.
Worth knowing: That unplug test is worth doing before any money is spent - it separates "the throttle body is faulty" from "the wiring to it is faulty", and those are wildly different bills. Whatever is repaired, the throttle must be re-adapted afterwards with diagnostic software (a Basic Settings routine on the engine ECU), or a perfectly good throttle body will still idle badly.
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 P2102 mean?
P2102 means Throttle Actuator A Control Motor Circuit Low. The voltage on this circuit is sitting near zero. Typically a short to earth, or a sensor that has failed to its low end.
Can I drive with P2102?
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.