31 High

Johnson Starley 31 Fault Code

The Johnson Starley 31 fault code means: your boiler has detected a problem with the internal temperature sensor that monitors your heating water, meaning it cannot safely regulate how hot the radiators get.. It appears on 10 Johnson Starley models 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: Centra heating supply sensor error (open or short)
Typical repair cost £120-190 (including labour)

Engineer required

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

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Johnson Starley models that show the 31 fault code

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

Source

Johnson Starley 31 fault code information on this page is sourced and cross-checked against the official Johnson Starley service / installation manuals for each affected model.

Reviewed by the BoilerFaultCodes Editorial Team · Last reviewed 27 April 2026