Bosch Washer E25 Error — Turbidity Sensor Fix

What it means

Bosch washer E25 error (also F25) means a turbidity sensor issue — Bosch's specific code for the optical sensor that measures water clarity (used to determine when rinse water is clean enough).
The sensor is either blocked with detergent and lint residue, or has failed.

Affected Models

Bosch Serie 2 / Serie 4 / Serie 6 / Serie 8 washing machines
Bosch Logixx, Maxx, Classixx ranges (older naming)
Bosch WAW, WAT, WAY, WAQ model series
Bosch Varioperfect washers
Same codes appear on Siemens and Neff washers (shared platform)

Common Causes

Turbidity sensor lens coated with detergent / softener residue
Sensor blocked by lint build-up
Sensor wiring loose at the control board
Sensor itself failed (rare — sensors are robust)
Drain hose blocked, dirty water sitting in sensor area

How to Fix It

Run a hot service cycle with descaler.

Run a 90°C cycle empty with a descaling tablet or two cups of white vinegar in the drum.
The hot detergent-and-vinegar solution often dissolves residue off the turbidity sensor and restores function.
This is the easiest E25 fix to try first.
Clean the pump filter and lower drain.

At the front bottom of the washer, open the access panel and remove the pump filter.
Clean off any lint or debris.
Sometimes the turbidity sensor sits near this area and benefits from the same clean.
Check detergent dose.

Reduce detergent to half the box recommendation.
Overdosing creates excessive suds and residue that build up on the turbidity sensor over time.
Switch to a high-efficiency detergent if you're not already using one.
Call a technician.

If hot service cycles and pump cleaning don't clear E25, the sensor may need replacement.
This is technician-level work — back panel comes off to access the sensor housing.
Part is moderate cost (£30–£50).

When to Call a Professional

Turbidity sensor cleaning is owner-doable on most models — sometimes via the pump filter access.
Sensor replacement is technician-level if cleaning doesn't help.

Frequently Asked Questions

What does the turbidity sensor in a Bosch washer actually do?

It measures how cloudy the rinse water is.
Cloudy water means there's still detergent or dirt suspended in it; clear water means the rinse is complete.
The control board uses the sensor's reading to decide whether more rinses are needed — saving water and energy when one rinse is enough, adding rinses when the load is heavily soiled.
When the sensor fails (E25), the control board can't make this decision and stops the cycle.
The sensor itself is a small optical device with an LED on one side and a light receiver on the other; residue or lint on either side blocks the light and triggers E25.