Bosch Washer Error Code Er:20

Er:20 on a Bosch washer indicates that the machine has detected excessive foam inside the drum during a wash or rinse cycle. The washer uses pressure and sometimes optical sensors to monitor water and foam levels inside the tub. When foam accumulates beyond the acceptable threshold, the control board triggers Er:20 to halt normal operation and prevent foam from being pushed into the drain pump, motor components, or pressure sensor lines, which could cause damage or inaccurate water level readings.

The most common root cause is the use of conventional detergent in a high-efficiency (HE) front-load or sensor-based top-load washer. Standard detergents produce significantly more suds than HE formulas, and even a small amount can overwhelm the low-water wash environment these machines use. Overloading the detergent dispenser beyond the recommended fill line is another frequent contributor, even when using HE detergent. Residue buildup inside the dispenser drawer can also cause detergent to release unevenly during the cycle, creating foam spikes.

When Er:20 appears, the washer will typically pause the cycle and may run additional rinse sequences automatically to reduce foam levels before resuming or draining. If the foam clears, the machine may continue on its own. Repeated occurrences of this error can point to a habitual overdosing problem or, less commonly, a contaminated drum from a product like fabric softener or a cleaning agent that was not fully rinsed from a previous cycle.