E55 Boiler Fault Code: What It Means on Every Brand

The E55 fault code appears on 2 brands — Baxi and Potterton — and it does not mean the same thing on each. The same two or three characters can signal a pressure problem on one boiler and an ignition fault on another, so identify your brand first and use the table below to jump to the right page.

Up to: Lockout — engineer likely 2 brands use this code Meaning differs by brand

Which brand is your boiler?

The brand is printed on the front casing. Tap your brand for the full causes, fixes and repair costs.

Brand	What E55 means	Severity	DIY?
BBaxi	The E55 code on a Baxi boiler indicates that the boiler's internal electronics have detected a communication failure. Full guide →	Lockout — engineer likely	No
PPotterton	The E55 code on a Potterton boiler is the appliance's way of flagging that it needs recalibration. Full guide →	Engineer may be needed	No

E55 brand by brand

Baxi E55

The E55 code on a Baxi boiler indicates that the boiler's internal electronics have detected a communication failure. In plain terms, the boiler's printed circuit board (PCB) has lost reliable contact with one or more of its connected components — such as the gas valve, pump, or a sensor — and has shut the boiler down as a precaution. In some cases E55 is also triggered when the gas valve requires re-calibration, meaning the valve is present and connected but is not responding within the parameters the PCB expects. Either way, the boiler cannot safely fire until the underlying electronics issue is resolved.

Causes, fixes & costs for Baxi E55 → · All Baxi codes

Potterton E55

The E55 code on a Potterton boiler is the appliance's way of flagging that it needs recalibration. In plain terms, something within the boiler's internal settings has drifted out of the acceptable range — this most commonly relates to combustion parameters such as the gas-to-air ratio, but can also involve sensor readings or control board data. The boiler raises E55 to warn that it cannot guarantee it is operating safely and efficiently without a calibration check, and in most cases it will lock out or restrict operation until the issue is addressed. This fault appears across several Potterton ranges including the Promax, Ultra, Gold, and Titanium series.

Causes, fixes & costs for Potterton E55 → · All Potterton codes

Frequently asked questions

Is the E55 fault code the same on every boiler?

No. E55 means different things on different brands — see the table above. Always identify your boiler's brand (it is printed on the front casing) before acting on any advice about the code.

Can I fix a E55 fault myself?

Not usually. On every brand listed, E55 points to a fault that needs a suitably registered engineer to diagnose and repair. A single reset to rule out a transient glitch is reasonable; repeated resets are not.

Who should I call about a E55 fault?

For gas boilers, a Gas Safe registered engineer — it is a legal requirement for any work on the appliance. If you smell gas at any point, leave the property and call the National Gas Emergency line on 0800 111 999.

General guidance only — not a substitute for professional advice, and not certified by a registered engineer. Any work on a gas appliance must be carried out by a Gas Safe registered engineer. If you smell gas, call 0800 111 999.