Error E.02 – .17

Safety first

1) If you smell gas: do not operate electrical switches, do not use phones or anything that might create a spark. Open windows, leave the property immediately and call the national gas emergency number. 2) If there is any sign of a leak, flame, or carbon monoxide (soot, staining, fumes, headaches), turn the boiler off at the external isolator and evacuate; call a Gas Safe engineer or emergency services.

Initial homeowner checks (safe, non-intrusive)

1) Note the exact error code and take a photo of the boiler display and rating plate (model and serial). This helps the engineer. 2) Check the gas supply: confirm other gas appliances (hob) light normally. If there is no gas supply to the house, contact your gas supplier. 3) Check mains electricity to the boiler: ensure the fused spur or consumer unit hasn't tripped and the display is powered. 4) Check system water pressure on the boiler gauge: aim for 1.0–1.5 bar. If pressure is below 0.5 bar the boiler may not operate; topping up using the filling loop may be needed (only do this if you know how). 5) Try a controlled reset: press and hold the boiler reset button for 5–10 seconds and allow the boiler to attempt restart. If the fault clears and does not return, monitor the system closely. Do not repeatedly reset more than once or twice.

What not to do as a homeowner

1) Do not open the boiler casing or attempt to access the gas valve, PCB, fan or internal wiring. 2) Do not attempt to replace the gas valve, PCB or fan yourself. These are controlled-service items that must be worked on only by a Gas Safe registered engineer. 3) Do not keep resetting the boiler repeatedly — this can mask an intermittent fault and may be unsafe.

If the fault persists (professional diagnostics recommended)

1) Call a Gas Safe registered heating engineer and tell them the exact code E.02 – .17, model and serial, and the actions you’ve already taken. 2) The engineer will perform electrical checks: inspect wiring and connectors between PCB and gas valve/air-gas unit for loose connections, corrosion, or damage; check plug-in connectors are seated; check for water ingress or burn damage on the PCB. 3) They will measure the control voltages/signals to the gas valve and verify continuity and correct response. 4) They will test the air/gas unit (PU unit) including fan operation, ionisation/flame sensing, and the gas valve operation. 5) If necessary the engineer may swap or replace the PU/gas valve or PCB, but only after proper isolation, leak testing and commissioning.

Additional useful steps while waiting for an engineer

1) Record when the fault first appeared, any pattern (e.g. after power cuts, storms, or when demand for hot water started), and if any other codes have shown. 2) Keep the boiler switched off if repeatedly locking out and not supplying heating/hot water; you can re-enable briefly if safe and required, but follow engineer advice. 3) Have paperwork ready: installation date, last service date, and the engineer’s report if recent. This speeds diagnosis.

Summary recommendation

E.02 – .17 is a permanent communication/fault between the gas valve/air-gas unit and the PCB and is potentially unsafe to repair by non-professionals. Do basic, safe checks (power, gas supply, pressure, reset) but call a Gas Safe registered engineer to inspect wiring, test the PCB and gas/air unit and carry out any repairs or replacements.