E.01-.12 Boiler Fault Code: What It Means on Every Brand

The E.01-.12 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.01-.12 means	Severity	DIY?
BBaxi	Baxi's E-series codes are permanent lockout faults — the boiler has shut itself down and will not restart until the underlying problem is resolved and the reset button is pressed manually. Full guide →	Lockout — engineer likely	Some checks
RRemehashown as E.01.12	The E.01.12 code appears on Remeha boilers when the control board detects that the water returning from the heating circuit is registering a higher temperature than the water leaving the… Full guide →	Lockout — engineer likely	No

E.01-.12 brand by brand

Baxi E.01-.12

Baxi's E-series codes are permanent lockout faults — the boiler has shut itself down and will not restart until the underlying problem is resolved and the reset button is pressed manually. The two-part number after the dot narrows the fault right down: for example, E.01–.04 means repeated flame loss, E.01–.11 points to a fan speed problem, E.02–.07 flags low system pressure, and E.04–.08 indicates the boiler has reached an unsafe temperature. All codes in the E.01–E.12 family work the same way — the boiler locks out, displays the code, and waits. Common sub-codes you may see include: E.01–.02 (return sensor reading higher than flow sensor), E.01–.04 (flame lost five times in 24 hours), E.01–.05 (return temperature sensor open-circuit), E.01–.11 (incorrect fan speed or draught), E.01–.12 (return temp greater than flow temp), E.01–.17 (no circulation detected), E.01–.20 (flue gas temperature above 140°C), E.02–.07 (low or no system water pressure), E.02–.16 (onboard control unit time-out — possible PCB damage), E.02–.17 (communication lost between gas valve and PCB), E.04–.01 (flow sensor short-circuit), E.04–.02 (flow sensor open-circuit), E.04–.03 (critically high flow temperature due to poor circulation), E.04–.04 (flue temperature sensor short-circuit), E.04–.08 (maximum safe temperature reached — safety thermostat open), and E.04–.10 (failure to ignite — check gas supply).

Causes, fixes & costs for Baxi E.01-.12 → · All Baxi codes

Remeha E.01.12

The E.01.12 code appears on Remeha boilers when the control board detects that the water returning from the heating circuit is registering a higher temperature than the water leaving the boiler — the opposite of what should happen in normal operation. Because this relationship makes no physical sense under correct conditions, the boiler shuts down to protect itself and prevent inaccurate heat regulation. The root cause is almost always a faulty or mispositioned temperature sensor, a circulation problem, or low water volume in the system. This dot-notation fault code is used on the newer Remeha Ace range; if you own an older Avanta or Quinta, a similar underlying fault would appear as a different code format.

Causes, fixes & costs for Remeha E.01.12 → · All Remeha codes

Frequently asked questions

Is the E.01-.12 fault code the same on every boiler?

Broadly, yes — on Baxi and Remeha the E.01-.12 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.01-.12 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 E.01-.12 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.