Baxi E133 Fault Code: Gas / Ignition Fault

What does E133 mean on a Baxi boiler?

The E133 fault code is one of the most common errors on Baxi combi, system and heat-only boilers. It is an ignition lockout: the boiler asked for heat, went through its start-up sequence, but the flame-sensing electrode never confirmed that a flame had lit.

In plain terms, the boiler thinks it has no gas to burn — so it shuts down safely and locks out rather than keep trying.

Because the most common single cause is a problem with the gas reaching the burner, E133 is usually described as a gas supply or ignition fault. It does not always mean your boiler is broken. Sometimes the gas supply itself has been interrupted, and once that's restored a simple reset clears the code.

Safe checks you can do yourself

None of the steps below involve opening the boiler or touching anything gas-related inside it. If a check doesn't clear the fault, stop and book an engineer.

1. Check your gas supply is actually on

Because E133 is so often a gas-supply problem, start here:

• Are your other gas appliances working? Try the gas hob or another gas appliance. If nothing else gets gas either, the issue is your supply, not your boiler.
• Is the gas meter on? Check the emergency control valve (the handle on the pipe at your meter) is in the open/on position — the handle should be in line with the pipe.
• Prepayment meter? If you're on a pay-as-you-go gas meter, make sure you're in credit. Running out of credit is a very common cause of a sudden E133.

If you smell gas at any point, do not touch any switches. Leave the property, open doors and windows, and call the National Gas Emergency line on 0800 111 999.

2. Check for a frozen condensate pipe

In cold weather, the external plastic condensate pipe (the white or grey pipe running outside to a drain) can freeze and block, which can stop the boiler and trigger a lockout.

This is one of the few internal-ish issues you can safely tackle: thaw the outside section of pipe by pouring warm — not boiling — water over it, or holding a wrapped hot-water bottle against it. Never attempt to thaw or open any pipework inside the boiler casing.

3. Reset the boiler — once

If your gas supply is fine and there's no frozen pipe, press and hold the reset button on the front of the boiler for a few seconds (check your manual for the exact button). Give it a couple of minutes to attempt ignition again. If it fires up and stays running, the lockout was a one-off and you're done.

When it's a job for a Gas Safe engineer

If the E133 keeps coming back after you've confirmed the gas is on and reset once, the fault is inside the boiler's sealed combustion and gas circuit. This is gas work and must only be done by a Gas Safe registered engineer. You can check any engineer's credentials on the Gas Safe Register.

The kinds of things an engineer will investigate include:

• The gas valve — failing or stuck, so the burner gets no gas.
• The ignition and flame-sensing electrodes — worn, dirty, cracked or badly gapped, so no spark or no flame detection.
• The flue and air supply — a blockage or poor combustion stopping a stable flame.
• The condensate trap or pipework inside the casing.
• Gas pressure at the boiler — too low to sustain ignition.

These are not DIY repairs. Removing the casing or touching the gas valve, electrodes, flue or sealed circuit yourself is dangerous and illegal for an unregistered person.

What might a repair cost?

If the fix turns out to be a component replacement, the cost depends on the part. As a rough 2026 guide for an out-of-warranty boiler:

Typical job	Indicative cost
Engineer call-out / diagnosis	£70–£120
Replace ignition / flame electrode	£100–£200
Replace gas valve	£250–£450
Clear / replace condensate trap	£90–£180

Figures are indicative and vary by region, model and parts availability. This is exactly the kind of unexpected bill that boiler cover is designed to absorb: most policies include parts, labour and an annual service for a fixed monthly price, so a gas valve failure doesn't land as a one-off lump sum.

Is E133 worth taking out cover for?

A single E133 caused by a frozen pipe or a topped-up prepayment meter costs you nothing.

But when the cause is a failed gas valve or worn electrodes, you're looking at a repair that can run into the hundreds — and ignition components tend to fail on older boilers, often in winter when engineers are busiest. If you'd rather pay a predictable monthly amount than risk a surprise bill, it's worth weighing up whether boiler cover is worth it for your situation.

You can also browse the best boiler cover options or cheaper entry-level plans if you want basic protection.

Frequently asked questions

This article is general information, not advice. It reflects a selected panel of providers, not the whole market. Always have gas faults inspected by a Gas Safe registered engineer.