Worcester Bosch Greenstar 15sbi Fault codes & diagnostics

3 fault codes with plain-English explanations, severity ratings, DIY guidance, and repair cost estimates.

Regular Natural GasLPG 15 kW 1999-2005 Discontinued
GC Numbers 41-311-4341-311-45

Replaced by: Greenstar 15Ri

Download the Worcester Bosch Greenstar 15sbi manual The official installation & service manual (PDF) — the exact document these fault codes were verified against. PDF

This boiler uses LED flash patterns

Count the flashes in one repeating group before the pause. That number is your fault code. Do not reset until you have noted it. How to read fault codes →

Versions & GC numbers

Which version do you have?

The GC number on your boiler's data badge identifies the exact appliance and production years, as recorded in the UK Product Characteristics Database.

GC number Appliance (register name) Produced
41-311-43 15 Sbi RSF 1999–2005
41-311-45 15 SBi RSF 1999–2005
Just want the most common Worcester Bosch Greenstar 15sbi faults?
The top 6 problems in plain English — with causes, DIY checks and repair costs.
Fault codes

All 3 documented codes

Tap any card for details

LED / flash-pattern codes
LOCKOUT LIGHT FLASHING

Your boiler has stopped working because it failed to light or stay lit, which has triggered a safety shutdown.

High DIY-safe £120-350

What to check first

  1. Check if your gas supply is active and credit is on your meter
  2. Press the reset button once to see if the boiler restarts
  3. Ensure any external gas valves are in the open position

Parts commonly replaced

  • Spark electrode
  • Flame sense electrode
  • Gas valve
  • Ignition lead
Full explanation for LOCKOUT LIGHT FLASHING
Digital codes
lock-out

Your boiler has failed to ignite after several attempts and has switched itself off for safety reasons, meaning it cannot currently provide heat or hot water.

High Engineer only £120-250

Parts commonly replaced

  • Ignition electrode
  • Gas valve
  • PCB
Full explanation for lock-out
LOCKOUT LIGHT ON (CONSTANTLY)

Your boiler has detected that it is getting too hot and has automatically shut itself down to prevent damage.

High Engineer only £120-250

Parts commonly replaced

  • Overheat thermostat
  • Central heating pump
  • NTC sensor
Full explanation for LOCKOUT LIGHT ON (CONSTANTLY)