Bosch dishwashers must run a maintenance test to see if any errors have occurred. Once this test is run, a code will display on the LCD screen. You use this code to determine any problems or repairs that the dishwasher needs.
Hold the "Rinse" and "Regular Wash" buttons at the same time. Press the "On" switch and the lights will flash on the dishwasher. Press the "Rinse" and "Regular Wash" buttons again to activate the test mode. The dishwasher will go through a regular cycle and then a message will appear.
If a "0" code appears after testing, then there are no problems with the dishwasher. Simply press the "Off" button and testing mode will complete.
Codes "2" and "8" indicate heating problems with the dishwasher. Code "2" means that there's a general heating fault and the dishwasher heating element needs replacement. Code "8" means that the internal temperature sensor has shorted out and no longer operates.
The amount of water fill can cause two errors. Error "4" means there's a fill problem, where the water is filling too much or too little. There could also be a block in the dishwasher drain. Some models will display "F," which is the same error.
Bosch dishwashers use a water filter process known as the Aqua Sensor. When this fails to filter water or operate, the "1" error appears on the dishwasher. Replace your Aqua Sensor to correct this error.