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 article lists i40, i41, i43 and i44 as codes the display can show; the current user manual gives the range i41 to i44 and does not mention a bare i40 at all. Whichever yours shows, note it down exactly, because the engineer will ask.
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. The manual gives the family as i41 to i44 and the support article adds i40 itself, so write down what your machine actually displays.
Do the reset AEG publish for this code: pull the plug, or switch off at the fuse or isolator, and leave it for about five minutes before reconnecting.
Clean the filters thoroughly and check the sump for foam or debris. This is the other step in AEG’s own guidance and it is free — but treat it as ruling something out rather than as the expected fix. Then run a short programme and watch whether the fault returns at the same point in the cycle, which 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.
Get a qualified appliance engineer to look at your AEG i40
We do not pass enquiries to a repair firm, so there is no form here. When you book a qualified appliance engineer, tell them the make, the model and the exact code or message on the display, and ask whether they carry parts for this make — that is what turns one visit into a repair rather than a quote.
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 September 2026. Your quote may differ.
Own this appliance and had this code? . Nothing is published until a person has read it.
Related AEG fault codes
- i20Get it checkedThe machine could not drain. Two beeps on a model without a display, and the filter in the bottom of the tub is the first place to look.Related: same brand
- i30Stop — call an engineerThe anti-flood device has triggered — water has collected in the base of the machine. AEG say to close the water tap and call service.Related: same brand
- i10Get it checkedNo water is coming in. One beep on a model without a display, and AEG publish a pressure range you can test against.Related: same brand
- i50Get it checkedA wash pump fault, so water is not being driven round the spray arms. Needs an engineer, but AEG do not treat it as a hazard.Related: same brand
- i60Get it checkedThe water inside is too hot, or the sensor that measures it has failed. Note that AEG’s own index describes this one differently from the article behind it.Related: same brand
Own an AEG dishwasher? Save it and its codes come first next time.
Related guides
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 gives the range i41 to i44 as a malfunction of the water level detection sensor; the support article covers i40, i41, i43 and i44 together. 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.
Technical review
Not reviewed by an engineer
No engineer has read this page. Severity follows what the manufacturer publishes, and we would rather tell you that than let a byline imply a sign-off.
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
This page has not been reviewed by an engineer, and we would rather tell you that than imply otherwise. The severity rating follows what the manufacturer publishes: where they say isolate the appliance and call someone, so do we.