Low Information
S.02 on Glow-worm Flexicom sx

Your boiler is simply performing a routine preparation step by running its internal pump before ignition to ensure safe water flow.

Reviewed by the BoilerFaultCodes Editorial Team · Last reviewed

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

pump pre-run

What causes this fault?

This status occurs when the boiler detects a demand for heat and starts the internal pump to move water through the heat exchanger. It is a vital safety check designed to ensure there is sufficient water flow before the burner ignites to prevent the system from overheating. Once the electronics confirm the water is circulating correctly, the boiler will proceed to the ignition stage.

DIY fix possible

This fault may be fixable without an engineer. Check your manual first.

Find a Gas Safe engineer
Search the official register →

Related fault codes

S.00View →S.01View →S.03View →S.04View →

Related guides you might find useful

Banging / kettling / whistling noise

Each noise points to a different fault.

Read →

Boiler keeps cutting out

Lockout fault with a reset-needed pattern.

Read →

Is boiler cover worth it?

Break-even maths on monthly cover.

Read →