AEG i40 fault codewhat it means and how to fix it
A water level sensor fault — not a dirty filter, whatever the repair sites say. This is the code most commonly misreported online.
Take care
What i40 means
AEG give the i40 family as a fault in the pressure sensor and water level control, and the user manual is more specific still: a malfunction of the water level detection sensor. The machine has lost its ability to tell how much water is in the tub, which is why it stops rather than continuing to fill blind. This page carries a correction, because three of the most visible repair-company guides all state that i40 means the filter is not clean. It does not. Cleaning the filter appears in the official guidance as a first remedial step — worth doing, and free — but the fault AEG name is a sensor. The difference matters: telling somebody their machine is fine and just needs a rinse out, when the component that measures water level has failed, is how a fillable machine ends up overfilling. One quirk of AEG documentation is worth flagging so you do not go looking for something that is not there. The support site publishes the family label i40, but the user manual only lists i41, i43 and i44. The bare i40 looks like a category heading rather than something a current machine actually puts on its display, so note down exactly what yours shows.
What causes it
| Cause | What is actually happening | How likely |
|---|---|---|
| Water level or pressure sensor failed | What AEG actually name. The sensor that measures how much water is in the tub has stopped reporting usable values. | Common |
| Sensor chamber silted or blocked | Debris or scale in the small chamber the sensor reads through, so a working sensor gets a false reading. Cheaper than the part. | Occasional |
| Filter heavily clogged | Not the fault itself, but it appears as the first remedial step in AEG’s own guidance and it costs nothing to eliminate. | Occasional |
| Wiring or connector to the sensor | A corroded or loose connector in a damp environment. Frequently cheaper than the sensor and worth checking before parts are ordered. | Occasional |
What to try yourself
Note the exact code. AEG document i41, i43 and i44 individually in the manual even though the support site heads the group as i40, so write down what your machine actually displays.
Clean the tub filter thoroughly. This is the first step in AEG’s own guidance and it is free — but treat it as ruling something out rather than as the expected fix.
Switch off at the socket for a minute and restart, then run a short programme and watch whether the fault returns at the same point in the cycle. A consistent point is useful information for whoever comes.
If it repeats, book an engineer and quote the code and where in the cycle it stops. Do not accept a diagnosis of "just needs the filter cleaning" if you have already cleaned it.
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What it costs to fix
Typical repair cost
£0–£200
Time on site
20 minutes
Free if the sensor chamber is simply silted. A replacement pressure or level sensor is typically £100 to £190 fitted, depending on how much has to come apart to reach it.
Typical UK prices including parts and labour, updated August 2026. Your quote may differ.
What other owners found
Nobody has shared what worked for them on this code yet. If you have had it, you would be the first — and it genuinely helps the next person.
Related AEG fault codes
- F13Get it checkedMain board fault. Worth getting the price before the part, because a board can cost a serious fraction of a new machine.Related: control and power
- E5Get it checkedAn electronic control fault. Candy group five codes under this one meaning and route all of them to their service centre.Related: control and power
- E27Get it checkedThe mains voltage is too low. Bosch state plainly that this is not a fault on the appliance — you want an electrician, not an appliance engineer.Related: control and power
Common questions about AEG i40
Several sites say i40 means the filter is dirty. Are they right?
No. AEG state it is a pressure sensor and water level control fault, and the manual calls it a malfunction of the water level detection sensor. Cleaning the filter is a first step in the official advice, not the diagnosis. Three prominent repair-company guides get this wrong in the same way, which is why it is worth saying explicitly.
My machine shows i41, not i40. Is that a different code?
It is the same family and the same fault area. AEG’s manual lists i41, i43 and i44; the support site groups them under i40. Quote the exact one you see.
Is it safe to keep using it?
The machine has stopped itself, which is the sensible outcome — a dishwasher that cannot measure its own water level should not keep filling. It is not a hazard in the way a leak is, but it is not something to reset repeatedly either.
Sources and how we verified this
We establish the facts from the sources below and then write the explanation ourselves. We do not copy manufacturer wording and we do not host their manuals.
- Manufacturer support portal
- Manufacturer technical and service documentation
Checked by Appliance technical reviewer (Qualifications to be displayed on appointment) on 5 August 2026.