2 04 Low

Ariston 2 04 Fault Code

Also written as 204 — same fault.

The Ariston 2 04 fault code means: your boiler is having trouble communicating with the solar panel sensor, meaning it cannot accurately monitor the temperature of your solar water heating system.. It appears on 8 Ariston models in our database.

Monitor it

This is a minor fault. Keep an eye on it and mention it at your next annual boiler service. Reset the boiler and see if it clears.

Technical description: Solar collector temperature probe open / short circuit
Typical repair cost £120-220 (including labour)

Engineer required

This fault requires a Gas Safe registered engineer. Do not attempt gas-related repairs yourself.

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Ariston models that show the 2 04 fault code

Click a model for the full fault code list and model-specific repair notes.

Source

Ariston 2 04 fault code information on this page is sourced and cross-checked against the official Ariston service / installation manuals for each affected model.

Reviewed by the BoilerFaultCodes Editorial Team · Last reviewed 7 July 2026