Error E.04 – .17

Safety precautions:

- If you smell gas (rotten egg smell) or suspect a gas leak: do not operate electrical switches, do not use mobile phones or anything that could create a spark. Turn off the gas supply at the meter if you can do so safely, leave the building immediately and call the gas emergency service and a Gas Safe engineer.

- If you do not smell gas, work calmly and safely. Isolate the boiler power at the fused spur before touching the boiler casing or control panel. Do not open or attempt to repair gas components or internal valves unless you are Gas Safe registered.

Initial checks a homeowner can do:

1) Note the exact error code and any other codes or LED indicators and record when it first appeared and any recent events (power cuts, freezes, servicing, building work).

2) Check the gas supply to the property: confirm other gas appliances (hob, gas fire) work. If there is no gas to the house, contact your gas supplier.

3) Check the boiler is receiving mains power: display lit, timers/smart controls set correctly, and the boiler hasn’t been isolated at a consumer unit or switched off at a fused spur.

4) Check the boiler pressure gauge: aim for roughly 1–1.5 bar for a combi. Extremely low pressure can cause other faults; top up only if you know how and the system is cold. If pressure is very low (<0.5 bar) repressurise, then attempt a reset.

5) Inspect external flues, air vents and the area around the boiler for obvious blockages or damage. A blocked flue or external damage can generate related faults.

One controlled reset (homeowner step):

- Locate the boiler reset button (follow manufacturer guidance on front panel) and press/hold for the recommended time (typically 3–10 seconds). Only attempt a single reset after you have completed the initial checks and there is no smell of gas. If the code clears and the boiler runs normally, monitor for recurrence; if it returns, do not keep resetting.

Diagnostic information to gather before calling a professional:

- Exact model and serial number of the boiler and the error code (E.04 – .17).

- What you observed before the fault (power cut, noises, loss of hot water or heating, strange smells).

- Boiler pressure reading and whether you attempted to top up or reset, and how many times you reset.

- Any unusual sounds (fan noise, banging, repeated ignition attempts).

- Photos of the boiler display and labels can help the engineer diagnose faster.

Why a professional is needed and what they will do:

- E.04 – .17 points at a defective gas valve or gas/air unit, components that control gas delivery and combustion safety. These parts require specialist diagnostic tools and must be replaced or adjusted by a Gas Safe registered engineer.

- The engineer will check electrical connections to the gas valve, test control board communications, verify fan and air pressure circuits, measure ionisation/flame signals, confirm correct gas supply pressure, and if necessary replace the gas valve or gas/air assembly and then run combustion and safety checks.

- Do not allow anyone who is not Gas Safe registered to work on the gas parts. After repair the engineer will perform combustion testing and ensure the boiler is safe and correctly commissioned.

Final actions and advice:

- If the fault persists after your basic checks and a single reset, turn the boiler off and arrange for a Gas Safe engineer. Continuing to reset or run the boiler with a gas valve/combustion fault is unsafe.

- Provide the engineer with the recorded details and the exact error code to speed up diagnosis. Keep the boiler isolated and do not attempt internal repairs yourself.