E.04-.04 Boiler Fault Code: What It Means on Every Brand

The E.04-.04 fault code appears on 2 boiler brands — Baxi and Remeha — and on all of them it points to the same kind of problem. The details still differ by brand (thresholds, sub-codes, reset procedure), so use the table below to jump to the page for your boiler.

Lockout — engineer likely 2 brands use this code

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 E.04-.04 means	Severity	DIY?
BBaxi	The E.04 group on Baxi boilers represents permanent lockout faults — the boiler shuts down and will not restart on its own until the underlying problem is properly resolved. Full guide →	Lockout — engineer likely	No
RRemehashown as E.04.04	The E.04.04 code (and the closely related E4/E04 codes) appears across several Remeha boiler ranges, and its precise meaning depends on which model is displaying it. Full guide →	Lockout — engineer likely	No

E.04-.04 brand by brand

Baxi E.04-.04

The E.04 group on Baxi boilers represents permanent lockout faults — the boiler shuts down and will not restart on its own until the underlying problem is properly resolved. The sub-code -.04 specifically points to a fault the boiler's control system has detected within the gas valve circuit or the combined gas-and-air (venturi) unit. Other sub-codes in the same E.04 family give useful context: E.04-.00 means the gas valve has not been detected at all; E.04-.01 relates to a flow temperature sensor short-circuit; E.04-.12 indicates a false flame signal (ionisation current present when there should be no flame, or combustion gases out of ratio); and E.04-.17 flags a broader gas valve or gas-air unit problem. E.04-.04 sits within this same gas valve family — the boiler's safety system has identified something it cannot self-correct and has locked out to prevent unsafe operation. The boiler will remain off until the fault is cleared and the root cause addressed.

Causes, fixes & costs for Baxi E.04-.04 → · All Baxi codes

Remeha E.04.04

The E.04.04 code (and the closely related E4/E04 codes) appears across several Remeha boiler ranges, and its precise meaning depends on which model is displaying it. On the Quinta Pro and commercial Quinta range, E.04 or E.04.04 points to an abnormal heat exchanger temperature reading — either too high or too low — often caused by a faulty or poorly connected return temperature sensor, poor circulation, or low system pressure. On the Avanta and Avanta Plus range, the equivalent E4/E04 code signals an ignition lockout: the boiler has attempted to light more than five times without successfully establishing a stable flame, and has shut itself down as a safety precaution. Both faults are serious enough to stop the boiler running, but they have quite different root causes and fixes.

Causes, fixes & costs for Remeha E.04.04 → · All Remeha codes

Frequently asked questions

Is the E.04-.04 fault code the same on every boiler?

Broadly, yes — on Baxi and Remeha the E.04-.04 code points to the same class of fault, and the recommended response is similar. Model-specific details such as sub-codes and reset procedures still vary, so follow the page for your own brand.

Can I fix a E.04-.04 fault myself?

Not usually. On every brand listed, E.04-.04 points to a fault that needs a suitably registered engineer to diagnose and repair. A single reset to rule out a transient glitch is reasonable; repeated resets are not.

Who should I call about a E.04-.04 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.