E04 High

Johnson Starley E04 Fault Code

The Johnson Starley E04 fault code means: your boiler has detected that the internal fan, which safely removes waste gases, is not spinning at the correct speed to operate safely.. It appears on 5 Johnson Starley models in our database.

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.

Technical description: Fan speed incorrect
Typical repair cost £200-£450 (including labour)

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 →

Johnson Starley models that show the E04 fault code

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

Source

Johnson Starley E04 fault code information on this page is sourced and cross-checked against the official Johnson Starley service / installation manuals for each affected model.

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