P0628–P2633 Fuel Pump A Control 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 |
|---|---|---|
P0628 | Fuel Pump A Control Circuit Low | Investigate soon |
P2633 | Fuel Pump B Control Circuit Low | Investigate soon |
The definition
P0628: Fuel Pump A Control Circuit Low.
P0628 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. 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
Same circuit as the other fuel pump control codes: the command wire on which the engine ECU tells the in-tank pump's control module what to do. "Low" means the ECU saw that line pulled down towards earth when it should have been sitting higher, which points at a short to earth in the wiring or a fault inside the control module. Note that this is the thin command wire, not the heavy feed that actually runs the pump. The car may drive normally, crank for a long time, or cut out.
Most likely causes, in order
- Water or damp in the connector at the pump. Damp across the pins gives a leakage path to earth that behaves exactly like a short. Very common under the rear seat and in the boot floor on VAG, and usually traced back to a tank flange seal, a rear light seal or a blocked drain. Inspect and dry it out before condemning anything electrical.
- Wiring shorted to earth. Look where the loom passes through a grommet, over a bracket or under a seat rail - insulation rubs through and the wire touches bodywork. Flexing suspect sections while watching live data will often reproduce it. Suspect this strongly if anything has recently been fitted or removed under the seats or in the boot.
- Fuel pump control module failed internally. The output stage inside the module can fail short. Reasonable to suspect once the wiring between it and the ECU has been proven clean - but prove it first, because this is the expensive part and it is the one people replace too early.
- ECU-side output fault. Last on the list and genuinely uncommon. Remember that on VAG an engine ECU swap brings immobiliser adaptation and, on newer cars, component protection release with it, so it is never simply a swap.
Worth knowing: Find and repair the short before fitting a replacement control module - whatever destroyed the first one will destroy the second just as quickly, and these are not cheap parts. And do not live with it: a pump control that cuts out intermittently can stall the car in traffic.
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 P0628 mean?
P0628 means Fuel Pump A Control 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 P0628?
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.