P.04 Low

Glow-worm P.04 Fault Code

Also written as P04 — same fault.

The Glow-worm P.04 fault code means: your boiler is currently running a special testing mode designed for engineers to check the system's performance, which will automatically turn off on its own after fifteen minutes.. It appears on 11 Glow-worm 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: Chimneysweep function: If there is a domestic hot water demand, the product runs in domestic hot water mode and at maximum heat input. If there is no domestic hot water demand, the product runs with the partial heat load that is set via diagnostics code d.00 and in heating mode. The function is active for 15 minutes.

Engineer required

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

Find a Gas Safe engineer

Search the official register for a qualified engineer in your area.

Gas Safe Register →
Boiler cover options

Avoid the next call-out bill

A cover plan would handle faults like P.04: no call-out fees, no surprise bills.

Approved partner
Domestic Appliance Guard
Unlimited call-outs, 24/7 helpline, no price-hike promise
Get a quote →

Affiliate links. We may earn a commission at no extra cost to you.

Glow-worm models that show the P.04 fault code

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

Source

Glow-worm P.04 fault code information on this page is sourced and cross-checked against the official Glow-worm service / installation manuals for each affected model.

Reviewed by the BoilerFaultCodes Editorial Team · Last reviewed 7 July 2026