The boiler tried to light but did not detect a flame, so it has locked out on the gas supply for safety.
Most common on: Baxi 600, Baxi 800, EcoBlue, Platinum+, Duo-tec
E133 is the most common Baxi fault code. It means the boiler went through its ignition sequence but failed to establish or detect a flame, so the control board shut the gas valve and locked out. It is often described as a gas supply fault or ignition lockout.
It is a deliberate safety lockout rather than a random error — the boiler will not keep sending gas when it cannot confirm a stable flame. A single lockout can usually be cleared with a reset, but a boiler that shows E133 repeatedly has an underlying fault that needs a Gas Safe engineer.
Make sure a gas hob or another gas appliance lights. If nothing gets gas, the problem is the supply — check the gas cock at the meter is on and that a prepayment meter has credit.
The isolation lever under the boiler should be in line with the pipe (open). If it is turned across the pipe, the gas is shut off.
Press and hold the reset button for a few seconds. If the boiler fires and stays lit, it was a one-off lockout. If E133 returns, stop resetting it repeatedly.
In cold weather a blocked or frozen condensate pipe (the white plastic pipe running outside) can trigger a lockout. Thawing it can clear the fault — but if you are unsure, call an engineer.
Repeated E133 lockouts point to the electrode, gas valve, PCB or gas pressure — all of which need a Gas Safe registered engineer with the right test gear.
Work on the gas side of a boiler must be carried out by a Gas Safe registered engineer. The checks above are limited to safe, non-invasive things a homeowner can look at (pressure, resets, the gas supply) — if in doubt, stop and call an engineer.
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The boiler tried to light but did not detect a flame, so it has locked out on the gas supply for safety. E133 is the most common Baxi fault code. It means the boiler went through its ignition sequence but failed to establish or detect a flame, so the control board shut the gas valve and locked out. It is often described as a gas supply fault or ignition lockout.
You can try a single reset and the safe checks below, but Baxi E133 usually needs a Gas Safe registered engineer. Never work on the gas side of a boiler yourself — it is illegal and dangerous unless you are Gas Safe registered.
A recurring E133 means the underlying cause has not been fixed — most often no gas reaching the boiler (gas cock off, meter credit run out, or the wider gas supply interrupted). Resetting repeatedly will not solve it; get the boiler diagnosed properly.
See all Baxi fault codes.