Bosch Dishwasher E:28 and the aqua sensor that stopped reporting

What E:28 means

The aqua sensor is a light-based turbidity sensor. It passes a beam through the wash water to gauge how dirty it is, and the automatic programs rely on that reading to decide whether to run longer or add a rinse. With E:28 the sensor is returning nothing sensible. Bosch names three possibilities: a dirty window, a sensor that is dead or missing, or failing wiring. Cleaning the sump area is listed as one fix.

Common causes of E:28

Film of grease or scale across the sensor window
Sensor dead, or never refitted after earlier work
Cable from the sensor to the power module failing

✓ One safe check you can try

1. Unplug the dishwasher. 2. Remove the filters and clean the sump thoroughly, since the sensor window sits there. 3. Wipe away the greasy film with a soft cloth and warm soapy water. 4. Run an empty hot cycle with a dishwasher cleaner before assuming the sensor has died.

! Why to stop there

Scraping the sensor window with a hard tool scratches it and ruins its reading.
A sensor that was never put back after a repair needs reinstalling, not replacing.
A new sensor on a still-greasy sump will be blinded again within weeks.

Opening a panel yourself does not automatically cancel a manufacturer warranty, but it can cause accidental damage, and some manufacturers set their own service conditions. Check your warranty terms, or ask us, before deciding.

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Other Dishwasher codes

1Bosch Dishwasher Service Test Result 1: Aqua Sensor 2Bosch Dishwasher Service Test Result 2: Heating Group 4Bosch Dishwasher Service Test Result 4: Water Filling 8Bosch Dishwasher Service Test Result 8: Temperature Sensor 16Bosch Dishwasher Service Test Result 16: Spray Diverter E:30Bosch Dishwasher E:30, voltage too high and the machine shut down E:31Water in the zeolite container - Bosch Dishwasher E:31 FBosch Dishwasher F on an older display (water filling)

E:28E:28 questions

Will the dishwasher still wash with E:28?

Yes. Without the sensor, automatic programs fall back to fixed settings, so cleaning is less tailored. Many owners simply see longer or shorter cycles than expected.

How do I stop the film coming back?

Clean the filters regularly, use a quality detergent, and run a dishwasher cleaner every few months. Hard water scale and grease both cloud the sensor.

Is a new sensor expensive?

The part is a modest repair next to the bigger parts of a dishwasher, and we give you a written price before ordering. Cleaning is always the first and cheapest step.