Baxi E133 Fault Code: Gas Supply Fault

Baxi E133 Fault Code: What It Means and What to Do

Baxi E133 means the boiler could not establish a flame. Baxi's own fault table calls it a gas supply fault and points engineers to the power supply, the sensing electrode, the spark electrode and its cable. For homeowners, the first checks are the gas supply, especially a prepayment meter, and in freezing weather the condensate pipe. Reset once; if it returns, call an engineer.

Last updated: 8 October 2026

Get a quote

All gas work is carried out by Gas Safe registered engineers.

Get a quote for your boiler

Sending an enquiry is free and there is no obligation. Tell us the fault and your postcode, and we will be in touch.

What does E133 mean on a Baxi boiler?

Baxi’s published error code table lists E133 as “Gas supply fault”, with the engineer’s checks being the power supply, the sensing electrode, the spark electrode and its cable. In practice it means the boiler went through its ignition sequence and could not detect a flame, so it locked out for safety.

The name is a little misleading. “Gas supply fault” does not always mean the gas is off: a flame that lights but is not detected by the sensing electrode produces the same result as one that never lights.

What causes E133?

Gas not reaching the boiler. A prepayment meter out of credit is the most common simple cause. A closed gas valve, or a supply interruption in the area, will do the same.
Condensate problems. A frozen or blocked condensate pipe or trap can stop the boiler running normally, especially in a cold snap.
Spark electrode or cable. If the spark is weak or the cable is damaged, the gas will not light reliably.
Sensing electrode. A dirty, worn or misaligned sensing electrode cannot confirm the flame.
Power supply. Baxi includes it in the checks; an unstable or incorrectly wired supply can affect ignition.
Gas valve. Less commonly, the gas valve itself is at fault.

What can you safely check yourself?

Check other gas appliances. If the hob will not light either, it is a supply problem rather than the boiler.
Check your meter. Top up a prepayment meter and follow your supplier’s steps to restore supply.
In freezing weather, check the condensate pipe outside and thaw it with warm water. See frozen condensate pipe.
Reset once following your user manual.
Note when it happens: at every start, or only sometimes.

When should you get an engineer?

If the gas supply is fine and E133 comes back after a reset, the fault is with ignition or flame detection inside the boiler. The engineer will check the gas pressure at the boiler, inspect and test the spark and sensing electrodes and the cable, check the condensate trap, and test the gas valve. Electrodes are a common, often inexpensive repair. You will be given the price before any work begins.

If the same boiler also shows other codes, note them all in your enquiry, including any shown just before you reset.

Baxi E133 fault code: common questions

Which Baxi boilers show E133?

Baxi lists E133 in the fault table for many of its current boilers, including the Baxi 600 and 800, Duo-tec, Platinum, Assure and EcoBlue ranges, plus Potterton Assure and Main Eco Compact, which are made by the same group.

How do I reset a Baxi E133?

Use the reset button as your user manual describes, usually pressing and holding it for a few seconds. Reset once. Baxi boilers limit the number of resets, so if E133 returns, stop and send an enquiry.

Can a frozen condensate pipe cause E133?

It can stop the boiler running and lead to a lockout like E133, so in freezing weather it is worth checking the outside condensate pipe and thawing it with warm, never boiling, water before calling.