How much does it cost to fix Keston error code E 04?

Typical repair cost for the Keston E 04 fault is £120-250 including labour.

E 04 High

Keston E 04 Fault Code

Q: What does the Keston E 04 fault code mean?

Your boiler has detected that the power was turned off and back on again while it was already trying to deal with a fault, causing the system to lock itself for safety.

Also written as E04 — same fault.

The Keston E 04 fault code means: your boiler has detected that the power was turned off and back on again while it was already trying to deal with a fault, causing the system to lock itself for safety.. It appears on 3 Keston models in our database.

Technical description: Power has been reset whilst boiler was in lockout

Typical repair cost £120-250 (including labour)

Engineer required

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

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Keston models that show the E 04 fault code

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

Source

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

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