Bosch Washer E28 Error — Flow Sensor Fault Fix

What it means

Bosch washer E28 error (also F28) means the flow sensor is faulty — Bosch's specific code for the sensor that measures water flow rate at the inlet.
Either the sensor is reading wrong, the flow rate is genuinely outside the expected range, or the sensor wiring 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

Flow sensor wheel jammed by debris or limescale
Inlet hose mesh filter blocked — slowing flow below detection threshold
Flow sensor wiring loose at the control board
Flow sensor itself failed (rare)
Water pressure too low for accurate flow reading

How to Fix It

Clean the inlet hose mesh filter.

Turn off the tap and unscrew the inlet hose from the back of the machine.
Inside the connection port is a small mesh filter — pull out, rinse, refit.
A blocked filter slows flow below the sensor's detection range and triggers E28.
Check water pressure.

Turn the tap fully open.
If pressure feels weak at other taps too, the household supply is the issue — Bosch needs at least 0.5 bar.
Low pressure can read as 'no flow' to the sensor.
Power-cycle the washer.

Unplug for 60 seconds, plug back in.
One-off flow sensor glitches sometimes clear on a clean reboot.
Replace the flow sensor (technician).

If filter is clean and pressure is OK but E28 persists, the flow sensor itself has failed.
Sensor sits inside the inlet manifold — needs the back panel off for access.
Order matching part from Bosch parts.

When to Call a Professional

Owner can clean the inlet filter and check pressure; sensor replacement needs technician access to the inlet manifold.
Sensor part is moderate cost (£20–£40).

Frequently Asked Questions

What does the Bosch washer flow sensor actually measure?

It counts the rotations of a small paddle wheel inside the inlet manifold as water flows past.
Each rotation represents a known volume of water, so the control board can calculate exactly how much water has entered the tub — much more accurate than relying on time + pressure alone.
This lets Bosch adjust water use precisely for each cycle and detect inlet valve leaks (water flowing when it shouldn't).
When the sensor fails (E28), the control board loses precise flow data and stops the cycle to prevent over- or under-fill.