E02 Boiler Fault Code: What It Means on Every Brand

The E02 fault code appears on 5 brands — Biasi, Johnson & Starley, Keston, Ravenheat and Warmflow — and it does not mean the same thing on each. The same two or three characters can signal a pressure problem on one boiler and an ignition fault on another, so identify your brand first and use the table below to jump to the right page.

Up to: Stop & check now 5 brands use this code Meaning differs by brand

Which brand is your boiler?

The brand is printed on the front casing. Tap your brand for the full causes, fixes and repair costs.

Brand	What E02 means	Severity	DIY?
BBiasi	The E02 (sometimes displayed as ER 02) fault code means the boiler has gone into a hard lockout because its safety thermostat has triggered. Full guide →	Lockout — engineer likely	No
JSJohnson & Starley	E02 on a Johnson & Starley unit is a false flame lockout: the flame-supervision circuit reported a flame at a moment when no flame should exist — typically before ignition or after the gas… Full guide →	Lockout — engineer likely	No
KKeston	The E02 code on Keston boilers is an ignition-related lockout, but its precise meaning differs slightly depending on which model you have. Full guide →	Lockout — engineer likely	No
RRavenheat	The E02 code on a Ravenheat boiler signals a pump circulation fault. Full guide →	Lockout — engineer likely	Some checks
WWarmflow	The E02 code means your Warmflow boiler has detected that its internal water temperature has climbed to an unsafe level — typically around 95°C or above — and the built-in high-limit… Full guide →	Stop & check now	No

E02 brand by brand

Biasi E02

The E02 (sometimes displayed as ER 02) fault code means the boiler has gone into a hard lockout because its safety thermostat has triggered. This thermostat is a last-resort protective device: it cuts the boiler off when internal temperatures climb to a dangerous level, indicating that something is causing the heating circuit to overheat. Unlike a soft lockout, the boiler will not restart on its own — a manual reset is required. However, a reset only clears the display; if the underlying cause of the overheating is still present, the code will return.

Causes, fixes & costs for Biasi E02 → · All Biasi codes

Johnson & Starley E02

E02 on a Johnson & Starley unit is a false flame lockout: the flame-supervision circuit reported a flame at a moment when no flame should exist — typically before ignition or after the gas valve has closed. Controls treat phantom flame signals as seriously as missing ones, because a flame signal with the valve shut suggests either a supervision fault or, worse, gas burning when it should not be. The usual technical causes are benign: a leaking flame signal from a contaminated or damp electrode, condensate tracking across the electrode or its lead, or a fault in the sensing circuit on the board. The unit locks out and must be professionally checked rather than repeatedly reset.

Causes, fixes & costs for Johnson & Starley E02 → · All Johnson & Starley codes

Keston E02

The E02 code on Keston boilers is an ignition-related lockout, but its precise meaning differs slightly depending on which model you have. On the C36, E02 signals a 'false flame' — the boiler's control board is detecting a flame signal before ignition has even been attempted, which causes an immediate safety shutdown. On the C40 and C55 combi models, E02 means the boiler has tried to ignite several times in succession and failed on every attempt. In both cases the boiler enters a hard lockout and will not try again until the reset button is pressed. The underlying theme is the same: something has gone wrong with either the flame-sensing circuitry or the conditions needed to achieve a reliable flame.

Causes, fixes & costs for Keston E02 → · All Keston codes

Ravenheat E02

The E02 code on a Ravenheat boiler signals a pump circulation fault. The boiler's controls have detected that water is not moving adequately through the primary circuit — either because the pump has stopped, is turning too slowly, or is being obstructed. To prevent overheating and heat-exchanger damage, the boiler shuts itself down until the issue is resolved. On some Ravenheat models (particularly the CS 80/90, WH System, and WH 80/90 ranges) the same fault may appear as 02E rather than E02 — both mean exactly the same thing and the same diagnostic steps apply.

Causes, fixes & costs for Ravenheat E02 → · All Ravenheat codes

Warmflow E02

The E02 code means your Warmflow boiler has detected that its internal water temperature has climbed to an unsafe level — typically around 95°C or above — and the built-in high-limit thermostat has automatically cut the boiler off as a safety measure. This is a protective lockout, not a minor glitch. The boiler will not restart until the root cause of the overheating is identified and the high-limit stat is manually reset. Because Warmflow boilers (including the Agentis Series and GS25A) use a manual-reset safety device, you cannot simply press the standard reset button and expect the boiler to recover — the high-limit thermostat itself must be physically reset, usually via a small recessed pin or button inside the appliance casing. If the fault returns after resetting, an underlying problem is causing the boiler to overheat and it must be investigated by a qualified engineer.

Causes, fixes & costs for Warmflow E02 → · All Warmflow codes

Frequently asked questions

Is the E02 fault code the same on every boiler?

No. E02 means different things on different brands — see the table above. Always identify your boiler's brand (it is printed on the front casing) before acting on any advice about the code.

Can I fix a E02 fault myself?

On some brands there are safe homeowner checks first — typically system pressure, the condensate pipe in cold weather, and a single reset. The underlying repair usually needs a registered engineer. Never open the boiler casing yourself.

Who should I call about a E02 fault?

For gas boilers, a Gas Safe registered engineer — it is a legal requirement for any work on the appliance. If you smell gas at any point, leave the property and call the National Gas Emergency line on 0800 111 999.

General guidance only — not a substitute for professional advice, and not certified by a registered engineer. Any work on a gas appliance must be carried out by a Gas Safe registered engineer. If you smell gas, call 0800 111 999.