What this error means
Turbidity sensor fault — the water clarity sensor is not reading correctly
The E25 error means the turbidity sensor — Which measures how dirty the wash water is to optimise programme performance — is not functioning correctly. This is most commonly caused by the sensor window becoming coated with detergent residue or limescale rather than the sensor itself failing. Excessive foam from overdosing detergent is another frequent cause.
What you'll need first
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Step-by-step
Symptoms to look for
- E25 displayed during the wash or rinse phase
- Programme adding unexpected extra rinses or stopping during the rinse cycle
- Machine behaviour is inconsistent — sometimes completing normally, sometimes faulting
- Error appears more frequently when using heavily dosed or powder detergents
How to fix it
Add a washing machine cleaning tablet or 60 g of citric acid powder directly into the drum. Select a 90-degree cotton programme with no laundry inside and run the full cycle. The turbidity sensor sits in the water path and uses an optical beam to measure water clarity — if its window is coated with detergent film or limescale the beam is blocked, generating false fault readings.
If you routinely use more detergent than the amount indicated for your water hardness, excess foam coats the turbidity sensor and generates repeated false readings. After the service wash, reduce your dose to the line marked for your specific water hardness and load size.
With the machine unplugged, remove the rear panel by undoing the screws around its edge. The turbidity sensor is a small component mounted in the lower part of the drum area or on the sump hose, connected by a short wiring harness and identifiable by a small clear or translucent optical window on its face. Use a clean damp cloth to gently wipe the sensor window. Do not use abrasive pads or scouring materials.
While the rear panel is removed, inspect the electrical connector attached to the turbidity sensor. It should be firmly and fully seated with no corrosion or moisture on the pins. Disconnect the connector and press it firmly back in to ensure a solid contact.
Disconnect the sensor wiring connector and set a multimeter to resistance. Test across the sensor terminals — refer to the service documentation for your specific Siemens model for the expected resistance value. A completely open circuit reading (OL) across all terminal combinations indicates the sensor has failed and needs replacing.
Reassemble the machine, plug it back in and run a standard 40-degree programme with a small load. The turbidity sensor should allow the programme to proceed and make its automatic rinse adjustments normally.
When to call an engineer
- Turbidity sensor reads open circuit on a multimeter after cleaning and descaling
- Wiring to the sensor is visibly damaged, pinched, or the connector is corroded
- Fault returns within 2 to 3 cycles after a full service wash and sensor clean
- Sensor window is cracked or physically damaged and cannot be cleaned
Frequently asked questions
What does the turbidity sensor actually do?
Can I use the machine while E25 is showing?
Will using less detergent fix E25 permanently?
How often should I clean the turbidity sensor?
🎯 What is likely causing this fault?
⚠️ Estimates based on common faults — not a guaranteed diagnosis. Always verify before ordering parts.
Parts you may need
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Usually found on a label inside the door frame or on the back panel of the machine.
| Part | Approx. UK Cost | Find it |
|---|---|---|
| Turbidity Sensor | £40 - £50 | 🛒 Amazon UK → |
ℹ️ Prices are approximate. Always check the part number matches your model before ordering. Not sure of your model number? Find out how to locate it here.