E0 Boiler Fault Code: What It Means on Every Brand

The E0 fault code appears on 4 brands — Andrews, Baxi, Remeha and Viessmann — 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: Lockout — engineer likely 4 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 E0 means	Severity	DIY?
AAndrews	The E0 fault code on Andrews boilers most commonly points to a problem with the return or flow temperature sensor — the sensor may have failed, developed a short circuit, or become… Full guide →	Engineer may be needed	No
BBaxi	The E0 code on a Baxi boiler indicates that the control board has detected a problem with one or more of the boiler's temperature sensors (NTC thermistors). Full guide →	Lockout — engineer likely	No
RRemeha	The E0 fault code on Remeha boilers signals that the boiler's control board has detected a problem with one or more of the water temperature sensors — specifically the flow sensor, return… Full guide →	Lockout — engineer likely	No
VViessmann	The E0 code on a Viessmann boiler points to a problem with the LON (Local Operating Network) — a proprietary communication bus that links the boiler's main control unit to external modules… Full guide →	Engineer may be needed	No

E0 brand by brand

Andrews E0

The E0 fault code on Andrews boilers most commonly points to a problem with the return or flow temperature sensor — the sensor may have failed, developed a short circuit, or become disconnected from its wiring harness. On some Andrews model ranges, E0 can instead indicate an ignition lockout, meaning the boiler attempted to light the burner but no flame was detected. Because Andrews is a specialist commercial and semi-commercial brand with model-specific fault tables, the exact meaning can vary between product ranges. Always cross-reference with your specific Andrews installation manual or contact Andrews technical support to confirm which interpretation applies to your unit.

Causes, fixes & costs for Andrews E0 → · All Andrews codes

Baxi E0

The E0 code on a Baxi boiler indicates that the control board has detected a problem with one or more of the boiler's temperature sensors (NTC thermistors). These sensors continuously monitor water temperature at key points — typically the flow, return, and domestic hot water circuits — allowing the boiler to regulate output and trigger safety cutoffs. When the control board receives a reading that falls outside expected parameters, or no signal at all, it raises the E0 fault and locks the boiler out to prevent unsafe operation. Note: on newer Baxi models, this general sensor fault has been split into more specific codes — E20 (flow sensor), E28 (flue sensor), E40 (return sensor), and E50 (DHW sensor) — so if your display shows one of those, cross-reference your model accordingly. On older models that only display E0, any of those sensor circuits could be the source of the problem.

Causes, fixes & costs for Baxi E0 → · All Baxi codes

Remeha E0

The E0 fault code on Remeha boilers signals that the boiler's control board has detected a problem with one or more of the water temperature sensors — specifically the flow sensor, return sensor, or the boiler body temperature sensor. These NTC thermistors continuously feed temperature data to the PCB so it can regulate how hard the burner works. When a sensor reading falls outside the expected range — due to a short circuit, open circuit, or significant drift in calibration — the boiler shuts down as a precaution to protect the heat exchanger and other internal components. Heating and hot water will both stop until the fault is cleared.

Causes, fixes & costs for Remeha E0 → · All Remeha codes

Viessmann E0

The E0 code on a Viessmann boiler points to a problem with the LON (Local Operating Network) — a proprietary communication bus that links the boiler's main control unit to external modules such as heating zone controllers, cascade units, and Vitotronic control panels. When communication breaks down between the boiler and one or more of these connected devices, the boiler flags E0 and may enter a restricted control mode or begin to cool down. On certain Viessmann models, E0 can also be triggered when the fixed high-limit thermostat has activated or the internal fuse F2 has blown — both of which cause the boiler to shut down and cool. Because the exact diagnosis can differ between models, a Viessmann-trained Gas Safe engineer is best placed to interpret the code on your specific appliance.

Causes, fixes & costs for Viessmann E0 → · All Viessmann codes

Frequently asked questions

Is the E0 fault code the same on every boiler?

No. E0 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 E0 fault myself?

Not usually. On every brand listed, E0 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 E0 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.