Bosch Range Error Code ER12

ER12 indicates a mismatch between a relay port pin state and its corresponding software register value in the Electric cooktop MTwisT control system. The control board continuously compares the physical state of each relay output against what the firmware expects, and ER12 is displayed when those two values do not agree. This is a safety fault designed to prevent uncontrolled or unexpected burner operation. Resolving it typically requires diagnosing or replacing the cooktop control board.

No, you should not attempt to use the cooktop while ER12 is active. The error indicates a hardware-to-software synchronization failure in the relay control system, which means the range cannot reliably control burner power levels. Continued use under this condition could pose a risk of uncontrolled heating. Disconnect power to the range and contact a technician before resuming use.

Repair costs depend on the root cause. If only a wiring connection needs to be corrected, labor costs may be in the range of $100 to $200. If the MTwisT control board requires replacement, parts alone can range from $150 to $400 or more depending on the specific model, with additional labor costs on top of that. Getting a diagnostic assessment from a certified technician before authorizing repairs is recommended to avoid unnecessary part replacement.

Some instances of ER12 caused by a temporary power anomaly can be cleared by performing a power cycle, which involves turning off the range at the circuit breaker for several minutes and then restoring power. If the error returns immediately or persists, the repair likely involves inspecting wiring harness connections or replacing the MTwisT control board, which is a task best suited for a qualified appliance technician due to the complexity of the control system.

A power reset by switching off the circuit breaker for several minutes may clear ER12 if the fault was caused by a transient voltage event or a temporary software state corruption. However, if the underlying cause is a physically failed relay, a damaged control board, or a persistent wiring issue, the error will return after the reset. A reset is a reasonable first step but should not be relied upon as a permanent fix.