Boiler error codes explained: when to reset, when to worry

Codes that usually just mean low pressure

Worcester Bosch E9 / 1017, Vaillant F22, Ideal F1, Baxi E119: all of these usually mean system pressure has dropped too low. Top the system back up to about 1.2 bar using the filling loop and reset the boiler.

If the code returns within days, you have a leak — see our pressure-loss guide for what to check next.

Codes about ignition and gas supply

Worcester EA / 227, Vaillant F28/F29, Ideal L2, Baxi E133: the boiler tried to light and couldn't. First, check other gas appliances work and your prepayment meter (if you have one) has credit. In cold snaps, a frozen condensate pipe is a common cause — thawing the external pipe with warm (not boiling) water often fixes it.

One reset is fine. Repeated ignition lockouts need a Gas Safe engineer — persistent re-resetting can mask a real fault.

Codes that tend to be expensive

Vaillant F75 (pump/pressure sensor), Worcester E5/E9 overheat codes that recur, and any code pointing at the heat exchanger or main PCB are where repair bills climb. A PCB alone is often £300–£500 fitted; a main heat exchanger can be more.

On a boiler over 10 years old, one of these codes is usually the moment to price a replacement before spending on the repair — especially in winter, when a second failure is likely at the worst time.

The honest repair-or-replace test

Add up: the repair quote, your boiler's age, and whether it's out of warranty. A £400 repair on a 14-year-old boiler keeps a G-rated appliance limping along; the same £400 is roughly the efficiency saving a new A-rated boiler returns in its first couple of years, on top of a fresh 10–12 year warranty.