54 Low

Sime 54 Fault Code

The Sime 54 fault code means: your boiler is struggling to accurately read the room or outside temperature, which may cause it to turn the heating on or off at the wrong times.. It appears on 4 Sime 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: Influence of ambient temperature
Typical repair cost £120-200 (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 54 fault code

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

Source

Sime 54 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