Baxi Boiler Faults & Fault Codes: Complete Guide

How Baxi fault codes work

Baxi is one of the UK's longest-established boiler brands, and modern combi, system and heat-only models — including the popular 600, 800 and Platinum ranges — flash a fault code on the front panel when they lock out.

The codes nearly always start with an "E" followed by a number (for example E1, E110 or E133). The "E" simply stands for error; the number identifies the specific fault the boiler's control board has detected.

A lockout isn't the boiler breaking for no reason — it's the boiler protecting itself and you. Rather than carry on running with a sensor reading, a flow problem or an ignition fault, it stops and shows the code.

The trick is reading the code correctly, because the exact meaning can shift slightly between models and generations. The label inside your boiler's casing flap, or your user manual, is always the final word for your specific unit.

Common Baxi fault codes at a glance

The table below covers the Baxi codes homeowners land on most. Each row gives the plain-English meaning and, where we have one, a link to a dedicated guide with the full causes, safe checks and indicative repair costs.

Treat this as general guidance, not a diagnosis for your exact model — and remember that only the low-pressure codes (E1, E118, E119, E207) have a safe homeowner fix. The rest are flagged engineer-only for a reason.

If your code isn't listed, don't guess from a similar-looking one — the same number can mean different things across the 600, 800 and Platinum generations. Check the meaning printed in your boiler's own manual or on the inside of the casing flap.

Which model do you have?

Baxi sells several ranges, and the same code can read slightly differently depending on which one you own. Knowing your range helps you read the right list:

• Baxi 600 / 800 — the current mainstream combi, system and heat-only ranges. Most show full "E" codes on the display; note that some 600 Heat units use flashing green/red lights rather than a numbered code.
• Baxi Platinum+ — the higher-output range; you'll often see codes like E119 and E125 documented specifically for these models.
• Baxi Duo-tec — an older but very common range still in many homes; this is where you'll most often see E118 for low pressure and E168 as a board/communication fault.
• Baxi Megaflo — system boilers paired with an unvented cylinder; they share much of the Duo-tec code set.

The authority for your unit is the fault-code list printed on the label inside the casing flap and in your user manual — not a generic table. If you're booking an engineer, having the range and the exact code to hand saves a diagnostic visit.

Which Baxi faults can a homeowner safely deal with?

Only a short list is genuinely DIY.

Anything that touches the gas valve, the burner, the flame-sensing electrode, the flue or the sealed combustion circuit means taking the casing off and using test equipment — that is Gas Safe registered engineer work only, and it is both illegal and dangerous for an unregistered person to attempt.

The homeowner-safe checks are:

• Low pressure (E1, E118, E119, E207) — top up via the filling loop using the steps below.
• A single front-panel reset — for a lockout, press reset once and watch what happens.
• A frozen condensate pipe in cold weather — thaw the external plastic pipe with warm (not boiling) water. See our guide to a frozen condensate pipe.
• Power and controls — check the boiler has power, the fused spur is on, and the thermostat or programmer is calling for heat.
• Cold radiators with everything else fine — trapped air can be released by bleeding the radiators.

The reset-once rule

To clear a lockout, use the front-panel reset.

On most Baxi models that means either pressing and holding the dedicated reset button, or — on units with an on/off/selector dial behind the pull-down flap — turning the selector switch to the "R" (Reset) position and holding it for about 5 seconds until the boiler tries to relight.

Check your manual for which mechanism your model uses. Do this only once.

How to repressurise a Baxi boiler

For a low-pressure code such as E1, E118, E119 or E207, repressurising via the filling loop is a safe homeowner job. The gauge should read about 1 to 1.5 bar when cold, rising towards roughly 2 bar when hot.

Below about 1 bar is low; Baxi defines the point at which the boiler actually locks out and shows a low-pressure code (such as E118) as around 0.5 bar. If you're seeing the code, you're well below where the system wants to be.

1. Turn the boiler off and let it cool for a few minutes.
2. Find the filling loop — usually a silver braided hose with a valve (or two) underneath or near the boiler; some Baxi models have a built-in keyed loop.
3. Open the valve(s) slowly — you'll hear water flowing in.
4. Watch the gauge and stop at about 1.0–1.5 bar. Don't go past roughly 2 bar; over-pressurising can trip the safety valve.
5. Close the valve(s) firmly, switch the boiler back on, and reset once if the code is still showing.

If the pressure keeps falling over days or weeks, you have a leak or an expansion-vessel fault that needs an engineer — not endless topping up. Our guide to low boiler pressure explains what to look for.

E133: the one code with a homeowner-safe cause

E133 is worth singling out because it has three documented causes, and only one of them is safe for you to act on:

• Frozen external condensate pipe (homeowner-safe) — in freezing weather the white plastic waste pipe running outside can ice up and block, and the boiler locks out. This is the only E133 cause you can deal with yourself: thaw the exposed pipe with warm — not boiling — water (a hot-water bottle, a heat pack, or warm water from a watering can over the frozen section). Boiling water can crack the pipe. Baxi lists E133, E119 and E128 among the codes a frozen condensate pipe can throw. See our guide to a frozen condensate pipe, then reset once.
• Gas supply problem (engineer-only) — no gas, low gas pressure, a tripped meter or a supply issue means the boiler sparks but can't light. This is gas work.
• Ignition or flame-detection fault (engineer-only) — a worn spark or sensing electrode, or its wiring, so the boiler either won't spark or can't "see" the flame. Behind the casing, on the combustion circuit — Gas Safe engineer only.

So if it's a hard frost and your condensate pipe is iced up, thawing it and resetting once may clear E133. If there's no frozen pipe, or the code returns after one reset, stop — the remaining causes are gas and combustion faults for a Gas Safe registered engineer.

When to call a Gas Safe registered engineer

The pattern is consistent across Baxi faults: the water-side checks (pressure, bleeding radiators, power and controls) are yours; everything behind the casing is an engineer's. Call a Gas Safe registered engineer when:

• A code returns after a single reset, or the boiler keeps locking out.
• The fault points to a sensor (E20, E28, E54), the fan (E160, E413), circulation (E125), a control-board or communication issue (E104, E168), an overheat or flue overheat (E110, E120) or ignition/gas (E133) — all internal, sealed-circuit, flue or gas components.
• Pressure keeps dropping despite topping up, suggesting a leak or failed expansion vessel.
• You smell gas, see scorching or soot around the boiler, or a carbon monoxide alarm sounds — in that case treat it as an emergency first.

You can confirm any engineer's registration, including the specific gas appliances they're qualified for, at gassaferegister.co.uk. The Gas Safe Register replaced the old CORGI scheme in 2009 and is the only legal register for gas work in the UK.

Never attempt work on the gas valve, pipework, flue, sealed circuit, pressure relief valve or anything behind the casing yourself.

Could boiler cover help with Baxi repairs?

Most of the faults in this guide — a failed sensor, fan, pump or gas valve — are engineer-only repairs that can run from one to several hundred pounds as a one-off bill. That's where a policy earns its keep.

With boiler cover, a breakdown like an E160 fan fault or an E133 ignition fault is handled for the price of your monthly premium, and an approved engineer is sent out rather than you sourcing one yourself.

Cover isn't right for everyone, and the value depends on your boiler's age, the excess and what's excluded. Our guides to the best boiler cover and whether boiler cover is worth it walk through how to weigh it up. We're a comparison site showing a selected panel of providers, not the whole market — so always read each policy's terms before you buy.

Frequently asked questions