E12 High

Johnson Starley E12 Fault Code

The Johnson Starley E12 fault code means: your boiler's internal computer memory has encountered a digital error, meaning the system cannot load the settings it needs to operate safely.. It appears on 8 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: EEPROM lockout
Typical repair cost £250-450 (including labour)

Engineer required

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

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Johnson Starley models that show the E12 fault code

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

Source

Johnson Starley E12 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