i5 Low

Sime i5 Fault Code

Also written as I5 — same fault.

The Sime i5 fault code means: your boiler is currently displaying a status code that indicates it is in the process of calibrating or reporting its internal heating temperature settings.. It appears on 1 Sime model 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: Set of effective heating temperature

Engineer required

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

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Sime models that show the i5 fault code

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

Source

Sime i5 fault code information on this page is sourced and cross-checked against the official Sime service / installation manuals for each affected model.

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