202 Boiler Fault Code: What It Means on Every Brand

The 202 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: 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 202 means	Severity	DIY?
AAriston	Ariston fault code 202 belongs to the 200-series, which covers domestic hot water (DHW) circuit sensor faults. Full guide →	Lockout — engineer likely	No
CChaffoteaux	Fault code 202 on a Chaffoteaux boiler indicates that the control system has lost a reliable signal from the lower NTC temperature sensor (thermistor) fitted to the solar or hot water… Full guide →	Engineer may be needed	No

202 brand by brand

Ariston 202

Ariston fault code 202 belongs to the 200-series, which covers domestic hot water (DHW) circuit sensor faults. On most Ariston boilers, code 202 points to a short circuit on the DHW flow or temperature sensor — the component that detects when you open a hot tap and tells the PCB to fire the burner. When this sensor develops an electrical fault, the boiler cannot operate safely and will typically lock out, cutting off your hot water supply. On Evo-range models (Clas HE evo, Clas HE evo System, E-combi evo, and E-system evo), the same code instead relates to a fault with the bottom storage temperature probe, which monitors the temperature in the lower section of a stored hot water vessel. A small number of sources also associate code 202 with a flame detection or ignition lockout on certain variants. Because Ariston applies this code slightly differently across its product range, always check your boiler's specific manual if you are unsure which interpretation applies to your unit.

Causes, fixes & costs for Ariston 202 → · All Ariston codes

Chaffoteaux 202

Fault code 202 on a Chaffoteaux boiler indicates that the control system has lost a reliable signal from the lower NTC temperature sensor (thermistor) fitted to the solar or hot water storage cylinder. The controller expects a resistance reading within a specific range from this probe at all times; when it receives either no signal at all (open circuit — broken wire or failed sensor) or a near-zero resistance reading (short circuit — wiring fault or shorted sensor), it logs code 202 and may lock out the appliance. In plain terms, the boiler cannot accurately measure the temperature at the bottom of the storage cylinder and has stopped operating as a safety precaution. This fault is specific to Chaffoteaux models equipped with a solar or indirect storage cylinder and will not appear on heating-only combi installations.

Causes, fixes & costs for Chaffoteaux 202 → · All Chaffoteaux codes

Frequently asked questions

Is the 202 fault code the same on every boiler?

No. 202 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 202 fault myself?

Not usually. On every brand listed, 202 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 202 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.