302 Boiler Fault Code: What It Means on Every Brand

The 302 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 302 means	Severity	DIY?
AAriston	Fault code 302 on an Ariston boiler signals an internal communication error — the main printed circuit board (PCB) has lost the ability to exchange data correctly with another board or… Full guide →	Stop & check now	No
CChaffoteaux	Fault code 302 on a Chaffoteaux boiler indicates that the two internal electronic boards — commonly referred to as the GP board and the GIU board — have lost communication with each other. Full guide →	Lockout — engineer likely	No

302 brand by brand

Ariston 302

Fault code 302 on an Ariston boiler signals an internal communication error — the main printed circuit board (PCB) has lost the ability to exchange data correctly with another board or electronic component inside the appliance. This is a 300-series code, which places it firmly in the electronic control and PCB category rather than a sensor fault. It is worth noting that the flow temperature sensor has its own separate code (110), and the return probe has code 112 — code 302 is not a sensor reading fault but rather a breakdown in the electronic conversation happening between internal components.

Causes, fixes & costs for Ariston 302 → · All Ariston codes

Chaffoteaux 302

Fault code 302 on a Chaffoteaux boiler indicates that the two internal electronic boards — commonly referred to as the GP board and the GIU board — have lost communication with each other. This sits within a broader group of electronic board faults (codes 301 to 307), each pointing to a different aspect of PCB-related trouble. Code 302 specifically flags a breakdown in the internal communication link between these two boards, rather than a straightforward main board failure (which would typically show as code 303 or 307). It is not related to code 309 (a gas command fault) or 3P9 (a routine service reminder). When 302 appears, the boiler will usually lock out and stop functioning until the underlying cause is addressed.

Causes, fixes & costs for Chaffoteaux 302 → · All Chaffoteaux codes

Frequently asked questions

Is the 302 fault code the same on every boiler?

No. 302 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 302 fault myself?

Not usually. On every brand listed, 302 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 302 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.