High Lockout
Fault 13 / 159 on Worcester Bosch Greenstar CDi Compact

Your boiler's computer is confused because it has detected a change in its connected control components and needs to be told how to work with them again.

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

System configuration: BUS device changed or replaced. Check system configuration for heating circuit!

What causes this fault?

This fault occurs when the boiler's main control board loses communication with a connected component, such as a smart thermostat or a plug-in wiring module. It most commonly happens after a power cut, a surge, or when a new control device has been installed but hasn't been properly synced with the system. Essentially, the boiler has detected a change in its electronic 'nervous system' and has shut down as a safety precaution until the configuration is confirmed.

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 fault codes

208View →212View →

Related guides you might find useful

Boiler won't turn on — 9-step checklist

Work through these before the call-out.

Read →

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 →