Error E.01 – .20

Safety precautions:

1) If you smell gas or suspect a carbon monoxide problem (headaches, nausea, dizziness, soot or yellow flame), leave the property immediately, call the gas emergency number (in the UK 0800 111 999) and call 999 for life‑threatening symptoms. Do not attempt internal repairs.

2) If you are unsure or uncomfortable performing any step below, stop and call a Gas Safe engineer. Do not remove covers or work inside the boiler unless you are qualified.

3) Before doing any visual checks, switch off the boiler at the control panel and/or the fused spur and ensure you understand how to safely turn the appliance back on. Avoid repeatedly resetting the boiler — one reset is OK, repeated resets may cause further damage or mask a dangerous fault.

Initial checks a homeowner can safely do:

1) Check the boiler pressure gauge. Aim for around 1.0–1.5 bar when cold (Baxi guidance usually 1–2 bar). If pressure is very low (below 0.5 bar) top up using the filling loop if you know how — open the filling loop valves slowly until pressure reaches target then close valves fully. If you don’t know how, call an engineer.

2) Bleed radiators to remove any trapped air which can prevent circulation. After bleeding, re-check pressure and repressurise if needed.

3) Look at the external flue terminal to ensure it is not blocked by birds’ nests, leaves, or debris. Do not crawl onto roofs if unsafe; use binoculars or visually check from ground level if possible.

4) In cold weather check the condensate/drain pipe for freezing (common in winter). A frozen condensate can cause faults; thaw frozen pipe with warm (not boiling) water.

5) With the boiler on, listen and feel (carefully) the pipes for signs the pump is running: you should hear the pump and feel a temperature difference between flow and return pipes. If the pump is silent and pipes remain cold when the boiler calls for heat, circulation may be absent.

6) If you have never tried a reset, try one reset only: press and hold the boiler reset button (or use the selector to R and hold) for 5–10 seconds, then allow the boiler to restart. If the same E.01 – .20 fault returns immediately or repeatedly, do not keep resetting.

Specific diagnostic and fix guidance (when to call a professional):

1) If low pressure fixed the issue and the fault does not return, monitor pressure over a few days. If pressure drops repeatedly, call an engineer — this indicates a leak, faulty expansion vessel or other system fault.

2) If bleeding radiators and repressurising does not restore circulation or the pump appears not to run, call a Gas Safe engineer to inspect/replace the pump, check motor capacitor, wiring, zone valves and pump wiring. Pump replacement and internal electrical work must be done by a qualified engineer.

3) If the external flue was blocked and clearing it stops the fault, arrange a service/inspection. If the flue is clear but the fault persists, the flue thermistor (flue temperature sensor), fan or the gas/air unit may be faulty and require testing or replacement by an engineer.

4) If the fault message indicates a sensor issue or the flow/return temperatures look incorrect (return higher than flow or improbable readings), do not attempt to replace sensors yourself — contact a Gas Safe engineer to test sensors, wiring and PCB communications.

5) If the boiler has been overheating before the fault (unusual noises, boiling sounds, very hot flow pipes), switch the boiler off and call a Gas Safe engineer. Prolonged overheating can damage the heat exchanger and could create unsafe combustion conditions.

When to call a professional:

1) If the E.01 – .20 fault persists after the simple checks above (pressure, bleeding, flue clear, one reset).

2) If the pump is suspected faulty, if sensor or PCB faults are indicated, or if there are signs of flue or heat‑exchanger blockage.

3) If you smell gas or suspect carbon monoxide at any time.

Final notes:

- This fault often indicates either a serious circulation problem or a failed temperature/flue sensor. Both require a qualified engineer for safe and correct repair.

- Avoid repeated resets; do a single reset only after the basic checks.

- Use a Gas Safe registered engineer for diagnosis and repair of internal components, fan or gas/air unit, and for any work affecting combustion, the flue or gas connections.