301 Boiler Fault Code: What It Means on Every Brand

The 301 fault code appears on 2 brands — Ariston and Chaffoteaux — 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: Stop & check now 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 301 means	Severity	DIY?
AAriston	Fault code 301 on an Ariston boiler signals a problem with the EEPROM — the small memory chip embedded on the main printed circuit board (PCB) that stores the boiler's configuration… Full guide →	Stop & check now	No
CChaffoteaux	Fault code 301 on a Chaffoteaux boiler signals an EEPROM error on the main control board (PCB). Full guide →	Lockout — engineer likely	No

301 brand by brand

Ariston 301

Fault code 301 on an Ariston boiler signals a problem with the EEPROM — the small memory chip embedded on the main printed circuit board (PCB) that stores the boiler's configuration settings and operating data. When this chip fails to read or write correctly, the boiler's control system can behave erratically, leading to intermittent heating, unexpected shutdowns, or a complete lockout. The 300-series codes (301 through 307) all relate to the PCB and its electronic control circuitry, so if your display shows any code in this range, the boiler's 'brain' is the area under suspicion. Code 301 specifically points to the EEPROM itself rather than other board components, though in practice an engineer will assess the entire PCB during diagnosis. This fault applies broadly across Ariston's range — including the Clas, Genus, E-Combi, and similar models — as Ariston uses a consistent fault-code system across its boilers.

Causes, fixes & costs for Ariston 301 → · All Ariston codes

Chaffoteaux 301

Fault code 301 on a Chaffoteaux boiler signals an EEPROM error on the main control board (PCB). The EEPROM is a small memory chip embedded within the PCB that holds the boiler's factory configuration and operating parameters. When this chip becomes corrupted or fails, the boiler cannot read the settings it needs to run safely and will lock out completely. Codes 301 through 307 all relate to anomalies on the main PCB — ranging from communication faults to internal short circuits — but 301 specifically points to the EEPROM memory component. Expect no heating and no hot water until the fault is resolved.

Causes, fixes & costs for Chaffoteaux 301 → · All Chaffoteaux codes

Frequently asked questions

Is the 301 fault code the same on every boiler?

No. 301 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 301 fault myself?

Not usually. On every brand listed, 301 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 301 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.