High Lockout
76 on Worcester Bosch Greenstar Utility 18/25

Your boiler's main control board has detected a setup error, meaning it no longer recognises which specific model it is meant to be.

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.

Technical description

Incorrect SFC

What causes this fault?

This fault occurs when the boiler's main control board loses its identity and can no longer confirm the specific power output it should be producing. The most common reason is a hardware communication failure between the central circuit board and the small 'identity plug' that stores the unit's settings. In many cases, this is triggered by an electrical surge or a component failing due to age.

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.

Find a Gas Safe engineer
Search the official register →

Related guides you might find useful

Boiler keeps cutting out

Lockout fault with a reset-needed pattern.

Read →

Yellow or orange flame — CO safety

Safety-critical — turn off, read this.

Read →

When to replace your boiler

7 signs repair isn't worth it anymore.

Read →