i2 High

Sime i2 Fault Code

Also written as I2 — same fault.

The Sime i2 fault code means: your boiler has stopped heating your radiators because it is unable to accurately read the current water temperature inside the system.. It appears on 1 Sime model in our database.

Call an engineer soon

Book a Gas Safe engineer within 24 to 48 hours. Your boiler may be unsafe or could break down completely if left.

Technical description: C.H. 2 sensor temperature
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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Sime models that show the i2 fault code

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

Source

Sime i2 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