Error E2 223

Safety first: if you smell gas, leave the property immediately and call the gas emergency number. Switch the boiler off at the mains before attempting any inspections, and do not remove sealed panels or internal covers. If you are not a Gas Safe registered engineer, do not open the boiler or touch internal wiring, gas components, or the PCB.

Initial homeowner checks you can do safely:

1) Note the full fault display and cause code (E2 223) and take a photo of the display for the engineer. 2) Try a single reset: follow the GB162 reset procedure (press reset or hold the reset/return button for 3 seconds). If the code clears and the boiler runs normally for a period, this suggests an intermittent connection. Do not repeatedly reset more than once or twice. 3) Check system water pressure on the gauge; low pressure (below about 1 bar) can cause sensor/operation anomalies on some faults. If pressure is low, re-pressurise the system to the recommended level using the filling loop according to the boiler handbook. 4) Visually inspect any external wiring you can safely access (room thermostat, programmer and obvious external wiring into the boiler) for loose connectors or damage. Do not probe inside the casing.

What a qualified engineer will do (diagnostic and fix steps):

1) Isolate and make the appliance safe, then remove the necessary access panels. 2) Visually inspect flow sensor wiring, connector and code plug on the PCB for corrosion, damage, or a loose/disconnected plug. Re-seat connectors. 3) Measure the flow sensor circuit with a multimeter: check for open circuit, short to earth, and verify NTC resistance changes with temperature (confirm NTC behaviour—resistance should fall as temperature rises). 4) Check the related code plug and control module configuration to ensure the correct plug is fitted and recognised. 5) If wiring and connector are OK but the sensor is out of specification (open circuit, shorted, or inconsistent), replace the flow temperature sensor. 6) After repair/replacement, clear the fault and run the boiler through diagnostics: confirm flow temperature rises correctly, burner modulation behaves normally, and there are no further related cause codes. 7) If the sensor reading and wiring check OK but the fault persists, test the PCB inputs and A/D converters and consider control board faults as a root cause.

Important reminders: do not attempt sensor replacement or electrical tests unless you are a competent person and Gas Safe registered. Repeated resets without fixing the root cause may mask a developing fault and could lead to other damage. If the fault recurs after an engineer visit, keep a record of the codes, timing and any circumstances (e.g., after servicing or weather changes) to help diagnosis. Call a Gas Safe registered Worcester Bosch engineer to carry out the internal checks and any replacement work.