Bosch Washer Error Code F:31

The F:31 error code on a Bosch washer indicates that the water level inside the drum has exceeded the maximum allowable overflow threshold. This is a critical safety condition: the machine has detected more water than it should ever contain, and it triggers this fault to prevent flooding. The water level monitoring system on Bosch washers relies on a pressure sensor (also called a pressure switch or pressostat) connected to a small hose that runs to the bottom of the tub. As the tub fills, air pressure builds in that hose and signals the sensor, which in turn tells the control board when to cut off the water supply.

When F:31 triggers, one of three primary faults is typically responsible. First, the inlet solenoid valve may be stuck in the open position, allowing water to continue entering the tub even after the fill cycle should have ended. Second, the pressure sensor itself may be miscalibrated or faulty, causing it to send incorrect water level readings to the control board. Third, the small hose connecting the tub to the pressure sensor may be kinked, clogged, or disconnected, which prevents accurate pressure readings and can cause the machine to misread the actual water level.

Additional contributing factors include a failed drain pump that is unable to remove excess water, a blocked or improperly routed draining hose that creates backflow or drainage resistance, or damage to the wire harness connecting any of these components to the main control board. Because an overflow condition can damage the motor, bearings, and electronics if the machine continues to operate, the washer will typically suspend the cycle and lock out operation until the fault is resolved and cleared.