5P2 Boiler Fault Code: What It Means on Every Brand

The 5P2 fault code appears on 2 boiler brands — Ariston and Chaffoteaux — and on all of them it points to the same kind of problem. The details still differ by brand (thresholds, sub-codes, reset procedure), so use the table below to jump to the page for your boiler.

Lockout — engineer likely 2 brands use this code

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 5P2 means	Severity	DIY?
AAriston	The 5P2 fault code means your Ariston boiler attempted to light the burner twice and failed on both occasions, triggering a full safety lockout. Full guide →	Lockout — engineer likely	Some checks
CChaffoteaux	The 5P2 code appears on Chaffoteaux boilers when the burner fails to light on its second ignition attempt — or, in some cases, when the boiler successfully ignited on that second try and… Full guide →	Lockout — engineer likely	Some checks

5P2 brand by brand

Ariston 5P2

The 5P2 fault code means your Ariston boiler attempted to light the burner twice and failed on both occasions, triggering a full safety lockout. Once in lockout, the boiler will not try again until it is manually reset. On some older Ariston display panels, the digit '5' can closely resemble the letter 'S', so you may see this displayed as 'SP2' — this is exactly the same fault, not a different code. The ignition sequence relies on a chain of components all working together: gas arriving at the correct pressure, the spark electrode firing reliably, the fan proving airflow, and the ionisation electrode confirming a stable flame. If any part of that chain fails twice in a row, the control board shuts everything down for safety and shows 5P2.

Causes, fixes & costs for Ariston 5P2 → · All Ariston codes

Chaffoteaux 5P2

The 5P2 code appears on Chaffoteaux boilers when the burner fails to light on its second ignition attempt — or, in some cases, when the boiler successfully ignited on that second try and has simply logged the event as a notification. Chaffoteaux boilers work through a staged ignition sequence: a first attempt is logged as 5P1, a second as 5P2, and a third failed attempt as 5P3. If ignition succeeds at any stage, the sequence stops there, so 5P2 does not always mean a fault is ongoing. However, 5P2 is classed as a non-volatile error, which means the boiler will not restart automatically — you must manually reset it. The display can be confusing because the digit '5' closely resembles the letter 'S', leading many users to read the code as SP2 rather than 5P2; both refer to the same fault. If repeated resets fail to clear the lockout, an underlying component or supply issue is almost certainly to blame.

Causes, fixes & costs for Chaffoteaux 5P2 → · All Chaffoteaux codes

Frequently asked questions

Is the 5P2 fault code the same on every boiler?

Broadly, yes — on Ariston and Chaffoteaux the 5P2 code points to the same class of fault, and the recommended response is similar. Model-specific details such as sub-codes and reset procedures still vary, so follow the page for your own brand.

Can I fix a 5P2 fault myself?

On some brands there are safe homeowner checks first — typically system pressure, the condensate pipe in cold weather, and a single reset. The underlying repair usually needs a registered engineer. Never open the boiler casing yourself.

Who should I call about a 5P2 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.