Boiler reports an internal control or sensor configuration fault; may limit hot water or heating output.

Safety: Switch off power at the isolator before removing any covers. Do not alter gas valve or combustion settings.

Steps:

• Check external sensors: If your Bosch boiler uses an outdoor temperature sensor or room controller (e.g. Bosch FW, CW series), verify they are correctly connected and not damaged. Inspect the two‑core cable for breaks.
• Verify configuration: Using the installer menu (see Bosch manual), confirm that the boiler is configured for the installed sensors (e.g. weather compensation enabled only if outdoor sensor is present). Correct any mismatched settings.
• Inspect PCB connections: With power off, check all low‑voltage plugs on the main control board: sensor harnesses, bus connections, and room thermostat terminals. Reseat connectors.
• Reset control: Perform a factory reset of control parameters if the manual allows. Re‑enter only basic settings (system type, DHW temperature, heating curve) as per installation guide.

Call a technician: If the error persists, the control PCB may be faulty. Replacement and re‑commissioning must be done by a Bosch‑trained heating engineer.