A01 High

Johnson Starley A01 Fault Code

The Johnson Starley A01 fault code means: your boiler's main control board has lost connection with the display screen, meaning they can no longer talk to each other to operate the heating.. It appears on 1 Johnson Starley model 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: Communication error between PCB and display
Typical repair cost £180-350 (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 A01 fault code

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

Source

Johnson Starley A01 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