High Lockout
1010 on Worcester Bosch Greenstar 8000 Life/Style

Your boiler's internal computer system has lost communication with its external controls or smart thermostat, meaning it cannot receive instructions to turn on.

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

No communication via EMS BUS connection

What causes this fault?

This fault occurs when the link between your boiler's main brain and your thermostat is physically broken or scrambled. The most common reason is a loose or damaged wire between the boiler and the control base, or a localized power surge that has caused the communication port on the internal circuit board to freeze.

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

2951View →2952View →

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 →