Bosch Dishwasher Error Code E28 — What It Means & How to Fix It

What Does This Error Mean?

Bosch dishwasher error E28 means the turbidity sensor — the sensor that detects how dirty the wash water is — has detected a fault or an out-of-range reading. The dishwasher uses this sensor to automatically adjust the wash cycle length and water temperature based on how soiled the dishes are. E28 is usually caused by a dirty sensor or a sensor fault.

Affected Models

Bosch 300 Series
Bosch 500 Series
Bosch 800 Series
Bosch SHPM88Z75N
Bosch SHXM88Z75N

Common Causes

The turbidity sensor is coated with grease or food residue and is not able to read water clarity accurately
Hard water scale has built up on the sensor lens, blocking its ability to detect water turbidity
The turbidity sensor has failed internally and needs replacing
The wire connector to the turbidity sensor has come loose, cutting off communication with the control board
A detergent film has built up on the sensor from using too much detergent repeatedly over time

How to Fix It

Turn off the dishwasher and unplug it or switch off the circuit breaker. Remove the lower rack and locate the turbidity sensor — it is typically a small optical sensor mounted in the sump area at the bottom of the tub.

Consult your model's manual or a quick search for your model number to confirm the exact location of the turbidity sensor.
Use a soft damp cloth to gently wipe the surface of the turbidity sensor. Remove any visible grease film, detergent residue, or scale buildup from the sensor lens.

The sensor works like a small window — if it is coated with grime, it cannot read the water clarity correctly.
Run a dishwasher cleaning cycle using a Bosch-approved cleaning tablet or a cup of white vinegar placed in the tub (no dishes). This removes scale and detergent film from the sensor and the rest of the dishwasher interior.

Bosch recommends running a cleaning cycle once a month. This single habit prevents most sensor-related error codes.
After the cleaning cycle, power cycle the dishwasher by unplugging it for 60 seconds. Plug back in and run a short cycle to test whether E28 returns.

If the error clears after cleaning, a maintenance schedule will prevent it from recurring.
If E28 persists after thorough cleaning, the turbidity sensor needs professional testing. A technician can confirm sensor failure and replace it — the sensor itself is not expensive, but accessing it requires some disassembly.

Turbidity sensors for Bosch dishwashers typically cost $20–$50 in parts.

When to Call a Professional

If cleaning the sensor does not resolve E28, the sensor has likely failed and needs replacement. The turbidity sensor is located near the sump on most Bosch models and requires disassembling the lower tub area — contact a Bosch-certified technician for this repair.

Frequently Asked Questions

What is a turbidity sensor and why does it matter?

A turbidity sensor is a small optical device that shines light through the wash water and measures how murky it is. The dishwasher uses this information to decide how long to wash and how hot to make the water. A dirty or faulty sensor can cause cycles to run too short (leaving dishes dirty) or too long (wasting energy).

How is E28 different from E27 on a Bosch dishwasher?

Both E27 and E28 relate to the turbidity sensor. E27 typically indicates the sensor is giving a reading that is out of range. E28 usually indicates a communication or circuit fault between the sensor and the control board. The initial fix steps — cleaning the sensor — are the same for both.

Will my dishes still get clean when E28 is active?

The dishwasher may stop mid-cycle when E28 is active, so dishes may not be washed at all. Even if the cycle completes, without a working turbidity sensor the machine cannot optimise the wash — dishes may come out with residue. Fix the sensor before relying on the dishwasher for sanitising items like baby bottles.