Bosch Dishwasher Error Code #A

Error code #A on a Bosch dishwasher with an Apexx display means the control board has detected a fault with the Aqua Sensor, indicated in red. The Aqua Sensor monitors how dirty the wash water is during a cycle. The fault can be caused by a dirty sensor lens, a failed sensor, or a wiring issue between the sensor and the control board.

Start by locating the Aqua Sensor, which sits in the sump area of the dishwasher, and clean its optical lens with a soft cloth to remove any grease or mineral deposits. If the code returns after cleaning, check the wiring harness connected to the sensor for loose plugs or visible damage. If the harness is intact and the code persists, the Aqua Sensor module itself likely needs replacement. A repair technician can confirm sensor failure with a resistance or voltage reading.

Replacing the Aqua Sensor is a moderate DIY repair. The sensor is located in or near the sump area and typically requires removing the lower spray arm and filter assembly to access it. The sensor usually clips or screws into place and connects via a wire harness plug. A homeowner comfortable with basic appliance disassembly can complete this repair, but if you are uncertain about working near electrical connectors inside the tub area, a technician is a reasonable choice.

It is not recommended to continue using the dishwasher normally with the #A code active. Because the Aqua Sensor controls how the wash cycle adjusts to water conditions, a fault can result in poor cleaning performance, incorrect water usage, or erratic cycle behavior. Address the sensor issue before running further cycles.

If the issue is a dirty sensor lens, the fix costs nothing beyond your time. A replacement Aqua Sensor module for a Bosch dishwasher typically costs between $20 and $60 for the part. If you hire a technician, expect to add $80 to $150 in labor depending on your area. A wiring harness repair or control board replacement would cost more and warrants a professional diagnosis first.