Performing a test cycle on a Bosch dishwasher is the best way to isolate the problem with its operation. The process is similar no matter which Bosch dishwasher one has, and the owner's manual that came with the dishwasher should have precise instructions for that specific model.
Holding down the Power Scrub Plus and Regular Wash, or analogous buttons depending on the model, then pressing the power button should cause the lights above the first two buttons to flash. Pushing those two same buttons again starts the test cycle. Once the test cycle has ended, the dishwasher indicates the area that contains the fault.
If the Bosch dishwasher does not have a display panel, the light turns on above the area containing the fault. If it lights up over the Clean button, a temperature sensor is causing the problem. Over Rinse/Dry, the light indicates a fault with the water sensor or the filling process. If the light appears over Wash, the heating process isn't working, so the heating element is likely the culprit.
Models that have display panels show codes after the test cycle to indicate the problem. If a 0 shows up, the cycle has not detected any errors, while 1 means a problem with the water sensor or filling, 2 means a fault with heating and 4 has to do with filling. An 8 indicates a problem with a temperature sensor.
If the dishwasher is not draining, start by checking if the dishwasher’s drain hose is clogged. Remove the drain hose from the dishwasher to clean it out. If the problem persists, test the drain pump’s motor with an ohmmeter to determine if it is defective. Replace a defective drain pump with a new one of the same kind.
If the dishwasher is noisy, first confirm that the noise is not being caused by loose dishes or clanging silverware inside the dishwasher. Remove the dish racks, and verify that there is no silverware, debris or bones at the base of the washer. If a loud vibration occurs during the filling cycle, the water inlet valve’s diaphragm may be damaged. Replacing the water inlet valve may solve the problem.
If the dishwasher is not filling with water, first investigate the water supply, and check if the main water valve is open. If the valve is fine, the dishwasher’s inlet valve may be causing the problem. A defective dishwasher’s water inlet valve is not repairable and has to be replaced. If the problem persists, confirm the dishwasher’s door seal is watertight and that the door catch is operating correctly.