Bosch E28 dishwasher: what it means & what to check

What E28 actually means

The dishwasher's water-clarity sensor — the one that judges how dirty the wash water is — isn't giving a reading the machine trusts.

Bosch dishwashers use a turbidity sensor (often called the aqua sensor) to look at how cloudy the water is and decide whether to extend the wash or change the water. When the control board sees a reading it can't make sense of, it logs E28. The usual complaint that brings it to our attention isn't the code itself but the results: plates coming out with food still on them and grubby water sitting in the tub.

What E28 looks like on a Bosch dishwasher

Most people find this page having searched for what the machine is doing rather than the code itself. On a Bosch dishwasher, E28 usually shows up as one or more of these:

Dishwasher not draining
Water left in the tub at the end of the cycle
Stops mid-cycle full of water
Standing water in the bottom
Not filling with water
No water going in
Takes for ever to fill
Stops right at the start of the cycle

Recognise any of those? That is this fault, and the rest of this page explains what causes it and what you can check yourself.

What usually causes it

The turbidity sensor itself has failed or drifted out of range
Grease, limescale or detergent film coating the sensor window so it can't read the water
Very dirty water in the tub because the filters and sump are clogged, which the sensor reads as an extreme
Wiring or connection fault between the sensor and the control board
Control board no longer interpreting the sensor signal correctly

What you can safely check yourself

Work through these in order. Anything beyond this — panels off, testing parts, anything to do with the wiring — is an engineer's job, and not one to attempt with the machine plugged in.

Lift out the filter assembly at the bottom of the tub, rinse it under the tap and clear any food debris from the sump area before refitting it
Check the spray arms spin freely and the holes aren't blocked with grit or bits of label
Run a hot cycle with a proprietary dishwasher cleaner — a heavy grease film through the machine is common where everything is rinse-free loaded, and it dirties the sensor as well as the tub
Make sure rinse aid and salt are topped up and the detergent isn't old or caked
Switch the machine off at the wall for a minute, then power up and start a fresh cycle to see whether the code returns

Common questions about Bosch E28

What does E28 mean on a Bosch dishwasher?

The dishwasher's water-clarity sensor — the one that judges how dirty the wash water is — isn't giving a reading the machine trusts. Bosch dishwashers use a turbidity sensor (often called the aqua sensor) to look at how cloudy the water is and decide whether to extend the wash or change the water. When the control board sees a reading it can't make sense of, it logs E28. The usual complaint that brings it to our attention isn't the code itself but the results: plates coming out with food still on them and grubby water sitting in the tub.

Can I fix Bosch E28 myself?

There are 5 checks you can safely do yourself first.

Lift out the filter assembly at the bottom of the tub, rinse it under the tap and clear any food debris from the sump area before refitting it.
Check the spray arms spin freely and the holes aren't blocked with grit or bits of label.
Run a hot cycle with a proprietary dishwasher cleaner — a heavy grease film through the machine is common where everything is rinse-free loaded, and it dirties the sensor as well as the tub.
Make sure rinse aid and salt are topped up and the detergent isn't old or caked.
Switch the machine off at the wall for a minute, then power up and start a fresh cycle to see whether the code returns.

This sometimes clears with those checks. If it comes back, it needs looking at properly.

How much does it cost to repair Bosch E28?

£66 including VAT for an engineer to come out and diagnose it, or £84 in total including VAT if it is put right on the visit and no parts are needed. Any parts needed are quoted on site before we fit them — you decide. Every repair carries a 90-day workmanship guarantee.

Tried the checks and it's still showing E28?

This sometimes clears with the checks above. If it comes back, it needs looking at properly. Then it wants someone who can open it up.

What it costs, before you call: the price is the same whatever the fault turns out to be — £66 including VAT for an engineer to come out and diagnose it, or £84 in total including VAT if it is put right on the visit and no parts are needed. Any parts needed are quoted on site before we fit them — you decide. Every repair carries a 90-day workmanship guarantee.

Our own engineers, not a call centre. We cover Nottinghamshire, Derbyshire and Leicestershire — most dishwasher faults are seen same day or next day.

Call 0115 648 0929 Book online — postcode and number is all we need

Outside our area? The explanation above still stands — take it to a local engineer and tell them the code. Knowing it saves them time and you money.

Other Bosch dishwasher codes

All Bosch fault codes and repairs →

What this looks like when it happens

dishwasher lights flashing

Repairs we cover near you

Written by the engineers at ASAP Repairs, 0115 648 0929. We repair these machines for a living in Nottinghamshire, Derbyshire and Leicestershire.

Bosch E28 error — dishwasher