Bosch Dishwasher Error Code M

Error code M on a Bosch dishwasher means the power supply relay is defective and has become stuck in a closed position. This relay is responsible for controlling power to major components inside the dishwasher. Because it cannot open on command, the dishwasher detects a loss of control and stops operation. This fault requires hands-on diagnosis and typically involves inspecting or replacing the control board.

No, it is not recommended to continue using the dishwasher once error code M appears. A relay stuck in the closed position can keep heating elements or motors energized beyond their intended run time, which creates a risk of overheating. Disconnect power to the appliance until the relay fault is diagnosed and repaired.

Repair costs vary depending on whether only the relay or the entire control board requires replacement, and on local labor rates. Control board replacements for Bosch dishwashers typically range from $150 to $400 or more for parts alone, with labor adding $100 to $200 depending on the service provider. Getting a diagnostic estimate before authorizing repairs is always a good idea.

This repair is not well suited for most DIYers because it involves diagnosing components on the main control board, which carries line-voltage electricity. A technician can use a multimeter to confirm whether the relay contacts are welded and determine if the control board needs replacement. Attempting this repair without proper electrical knowledge and safety precautions poses a real shock hazard.

Resetting the dishwasher will not resolve error code M. This fault reflects an actual physical failure of the relay component, meaning the hardware itself is defective. No software reset or power cycle will restore a relay whose contacts have welded together. The faulty component must be repaired or replaced.