Bosch E27 fault codewhat it means and how to fix it
The 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.
Take care
What E27 means
E27 is one of the most useful codes Bosch publish, because of a sentence most manufacturers would never write. Their manual gives the meaning as the mains voltage being too low and then adds, in their own words, that this is not a fault on the appliance. The instruction that follows is to contact an electrician and have the mains voltage and electrical installation checked. Bosch UK add a specific figure worth knowing: the mains voltage is usually below 170 volts when this appears. UK mains sits nominally at 230 volts, so 170 is a long way down and points at something real rather than a marginal reading. This matters commercially as well as technically. A reader who sees a fault code on a dishwasher naturally books a dishwasher engineer, and for this code that is money spent to be told the appliance is fine. The problem is in the wiring, the socket, or occasionally the incoming supply. If other things in the kitchen have been behaving oddly — lights dipping when something switches on, other appliances tripping — that is corroboration rather than coincidence, and it is worth mentioning to whoever you call.
What causes it
| Cause | What is actually happening | How likely |
|---|---|---|
| Extension lead or multi-way adaptor | The commonest and the easiest to fix. A dishwasher draws heavily while heating and these are not built for a sustained load of that size. | Common |
| Loose or failing socket | A worn socket or a loose terminal produces a voltage drop under load that a meter at rest will not show. | Common |
| Circuit overloaded or undersized | Several heavy appliances on one circuit, so voltage sags whenever they coincide. More likely in older properties. | Occasional |
| Incoming supply problem | Outside the property altogether. Rare, but it is the reason to mention any wider symptoms to the electrician. | Rare |
What to try yourself
Look at what the machine is plugged into. If it is an extension lead or a multi-way adaptor, move it to a wall socket of its own — that alone resolves a good share of these.
If there is any scorching, discolouration or a smell of hot plastic at the plug or socket, stop, switch off at the consumer unit and call an electrician. Do not plug it back in.Plug something else demanding into the same socket — a kettle is ideal — and see whether it behaves normally. A second appliance struggling points at the socket rather than the dishwasher.
Notice whether the problem coincides with other heavy appliances running. Voltage sag that only appears when the washing machine heats suggests an overloaded circuit.
Call an electrician rather than an appliance engineer. This is Bosch’s own instruction for this code, and an appliance repairer is not qualified to work on your house wiring anyway.
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What it costs to fix
Typical repair cost
£0–£200
Time on site
20 minutes
Free if it is an extension lead. An electrician replacing a faulty socket is typically £80 to £160. Investigating a circuit or supply problem properly costs more and is quoted after inspection.
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 Bosch 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
- i40Get it checkedA water level sensor fault — not a dirty filter, whatever the repair sites say. This is the code most commonly misreported online.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
Common questions about Bosch E27
Do I really not need an appliance engineer?
Not for this code, according to Bosch. Their manual says in terms that this is not a fault on the appliance and tells owners to contact an electrician and have the mains voltage and electrical installation checked. Booking an appliance engineer for E27 is a call-out fee to be told the machine is fine.
How low is too low?
Bosch UK say the mains voltage is usually below 170 volts when this code appears. UK mains is nominally 230 volts, so that is a substantial drop rather than a borderline reading.
Could it be a fault in the machine misreading the voltage?
It is possible, and an electrician confirming the supply is healthy is what establishes it. But Bosch’s starting position is the supply, and checking that first is both cheaper and the order they recommend.
My machine shows E:90-01. Is that this?
Yes, and E:9001 on a text display. Same code across display generations.
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 technical and service documentation
- Manufacturer support portal
Checked by Appliance technical reviewer (Qualifications to be displayed on appointment) on 5 August 2026.