Error E2 222

Safety first

- If the boiler is displaying E2 222 and you suspect an electrical fault, switch the boiler off at the room thermostat and the boiler mains isolator. Leave it off if you see burnt smells, smoke or visible electrical damage. Do not open or attempt internal electrical repairs if you are not qualified. Working on gas appliances and internal wiring is hazardous and should be done by a Gas Safe engineer.

Initial homeowner checks you can safely do

1. Note the exact error code, any LED behaviour and when it happens (on demand for heating, at DHW, or continuously). Write this down for the engineer.

2. Try a single controlled reset. Press and hold the boiler reset button for about 3 seconds and allow the boiler to attempt a restart. If the fault returns immediately or repeatedly, stop resetting and proceed to the next checks.

3. Check boiler water pressure on the front gauge. Very low or very high pressure can cause other faults; top up only via the correct filling link as per manufacturer guidance if pressure is below recommended levels.

4. Visually inspect accessible external wiring and pipework around the boiler for signs of water leaks, damaged or crushed cables, corrosion at connectors or damp ingress around the flow pipework. Do not remove covers or internal panels to trace wiring if you are not competent.

5. Check for recent events that could cause the fault: recent plumbing work, power surges, flooding, or freezing conditions that may have affected wiring or sensors.

Specific diagnostic and next steps (what an engineer will do)

- If your simple checks have not cleared the fault, call a Gas Safe registered engineer. Tell them you have an E2 222 flow temperature sensor shorted fault and provide any observations from the checks above. The engineer will:

- Isolate gas and electrical supplies and open the boiler safely.

- Visually inspect the flow sensor, its plug and harness and the circuit board connections for corrosion, water ingress or damage.

- Measure the NTC flow sensor resistance and check for short circuit or open circuit, and check continuity of the sensor wiring back to the control PCB.

- Check for any short to earth or damaged insulation on wiring and test the PCB inputs. If the sensor reads correctly but wiring or PCB is faulty the fault location will be addressed accordingly.

- Replace the flow temperature sensor and/or the wiring harness if they are found to be defective. If the PCB or burner control unit is at fault they will advise on the appropriate repair or replacement.

- Reassemble, restore supplies and run the boiler through several demand cycles to confirm the fault is cleared and the flow temperature reads normally.

Important notes and when to call a professional

- Do not repeatedly reset the boiler to clear the fault; a single reset to confirm the fault is acceptable but repeated resets can mask an electrical problem and are not a fix.

- Do not attempt to replace the NTC sensor, perform resistance testing inside the boiler, or work on the PCB unless you are a qualified, Gas Safe registered engineer. These actions involve both gas and electrical risks and may invalidate warranties.

- If the fault returns after basic checks, or if you find signs of water or electrical damage, leave the boiler off and book a Gas Safe engineer or an accredited Worcester Bosch service technician.

What to tell the engineer when you call

- Give the exact model and the error code E2 222, describe when it occurs (heating, hot water, boot-up), whether you performed a reset and what you saw, note any visible damage or leaks, and mention any recent work or power issues. This helps speed diagnosis and reduces visit time.

Following a professional repair, keep a note of the work carried out and ask the engineer to run the boiler through several cycles and show you that the fault has cleared before signing off.