Low Information
S.02 on Glow-worm Ultracom 2 CXI

Your boiler is performing a routine start-up check by running the internal pump for a few moments before lighting the burner.

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 isn't actually a fault, but rather a normal part of the boiler's ignition sequence. It occurs when the system starts a 'pump pre-run' to ensure water is circulating correctly through the heat exchanger before the gas burner is allowed to light. This safety check prevents the boiler from overheating during the initial start-up phase.

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 →

Is boiler cover worth it?

Break-even maths on monthly cover.

Read →

When to replace your boiler

7 signs repair isn't worth it anymore.

Read →