Medium
ST19 on Worcester Bosch Greenstar 15i System

Your boiler's internal communication system is experiencing a temporary glitch, preventing it from talking to its own controls or external thermostats correctly.

Reviewed by the BoilerFaultCodes Editorial Team · Last reviewed

Book a service

This fault should be looked at by a Gas Safe engineer within the next week or two. It may get worse if left.

What the manual says

Manufacturer manual

EMS bus connection

From this model's manual
Verified against the Worcester Bosch Greenstar I System installation & service manual, page 35.
Plain-English guidance below. Severity, DIY steps, costs and parts are our interpretation to help you act, not text from the manual.

Engineer required

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

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Related fault codes

ST18View →ST20View →

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