High
E004 on Navien NCB500 NCB500-1S+/30K

Your boiler is trying to start up for heating or hot water, but it is failing to light the gas flame after several tries.

Reviewed by the BoilerFaultCodes Editorial Team · Last reviewed

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.

What the manual says

Manufacturer manual

Unable to ignite the gas / Results in multiple unsuccessful ignition attempts.

From this model's manual
Verified against the Navien/Navien Ncb500 Combi Service Manual30k En 250331 Pdf installation & service manual.
Plain-English guidance below. Severity, DIY steps, costs and parts are our interpretation to help you act, not text from the manual.

Engineer required

This is a high severity fault. Stop using the boiler and call a Gas Safe registered engineer. Do not attempt gas-related repairs yourself.

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Related fault codes

E003View →E012View →E030View →

All 60 fault codes on the NCB500 NCB500-1S+/30K

Seeing a different code? Every code this model can display, in one place.

001003004012016030031046047109205218302352353407421515517593594615740782E001E003E012E016E030E031E046E047E109E110E205E218E291E302E351E352E353E407E421E434E439E441E445E480E515E517E593E594E598E615E740E782E783E787E788

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