Bosch Range Error Code ER26

ER26 indicates that the Electric cooktop MTwisT control system has detected a relay supply voltage that is too high during the off state of the control. This means voltage is present on a circuit where it should read near zero when the cooktop is off. The range flags this fault to prevent potential damage to the control electronics or unintended heating of a cooktop zone.

It is not recommended to continue using the cooktop while ER26 is active. The fault indicates an abnormal voltage condition in the control relay circuit, which could potentially lead to unexpected behavior of the heating zones or further damage to the control board. Discontinue use of the cooktop portion of the range until the fault has been diagnosed and repaired.

Start by measuring the incoming supply voltage at the range's terminal block using a multimeter to confirm it falls within the rated range for the appliance. If supply voltage is normal, the next step is to inspect the wiring harness between the power supply and the MTwisT control module for any damage or shorts. If wiring and supply voltage check out, the likely culprit is a failed relay or the MTwisT control board itself, which would require component-level testing or board replacement.

You can attempt a reset by cutting power to the range at the circuit breaker for several minutes and then restoring it. However, if the underlying cause, such as an overvoltage condition or a failed relay, has not been resolved, the ER26 code is likely to return. A reset alone is not a fix and should be followed by a proper diagnosis of the supply voltage and control components.

Repair costs vary depending on the root cause. If the issue is a faulty MTwisT control board, parts alone can range from roughly $150 to $400 or more depending on the specific model, with additional labor costs if a technician performs the repair. If the cause is an overvoltage issue from the home's electrical supply, an electrician may need to address the panel or circuit, which carries its own separate cost range.