BoilerFaultCodes 226
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Worcester Bosch Greenstar 21i System ErP Fault codes & diagnostics
13 fault codes with plain-English explanations, severity ratings, DIY guidance, and repair cost estimates.
System Natural GasLPG 2015-present
GC Numbers 41-406-2941-406-30
Download the Worcester Bosch Greenstar 21i System ErP manual
PDF
Versions & GC numbers
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Severity at a glance
Each cell = one fault code. Hover to identify. 5 High
2 Medium
6 Low
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 |
|---|---|---|
| 41-406-29 | Greenstar 21i System ErP | 2015–present |
| 41-406-30 | Greenstar 21i System ErP LPG | 2015–present |
Appliance names and production years are taken from the UK Product Characteristics Database (the SAP/SEDBUK register). Where a GC number is also printed in this model's own manufacturer manual, both sources were checked to agree.
Just want the most common Worcester Bosch Greenstar 21i System ErP faults?
The top 6 problems in plain English — with causes, DIY checks and repair costs.
Fault codes
All 13 documented codes
Tap any card for details
235 Your boiler's internal computer is reporting that a piece of hardware is using software that doesn't match the rest of the unit, preventing it from functioning.
Your boiler's internal computer is reporting that a piece of hardware is using software that doesn't match the rest of the unit, preventing it from functioning.
Parts commonly replaced
- HCM (Heatronic Control Module)
328 Your boiler's computer is struggling to get a steady power supply from your home's electricity, causing it to stop work to protect its internal parts.
Your boiler's computer is struggling to get a steady power supply from your home's electricity, causing it to stop work to protect its internal parts.
Parts commonly replaced
- Printed Circuit Board (PCB)
- Wiring harness
356 Your boiler is struggling because the electricity supply feeding it is weak, uneven, or cutting out momentarily.
Your boiler is struggling because the electricity supply feeding it is weak, uneven, or cutting out momentarily.
Parts commonly replaced
- Printed Circuit Board (PCB)
- Power cable/fused spur
Related codes
360 Your boiler's main electronic brain has lost its configuration or cannot read its own memory properly, so it has shut down for safety.
Your boiler's main electronic brain has lost its configuration or cannot read its own memory properly, so it has shut down for safety.
Parts commonly replaced
- PCB
- Heat Circuit Module (HCM)
Related codes
363 Your boiler is struggling to detect that the flame is lit, so it has safely shut itself down to prevent wasting gas.
Your boiler is struggling to detect that the flame is lit, so it has safely shut itself down to prevent wasting gas.
Parts commonly replaced
- Ignition electrode
- Ionisation probe
- PCB
Related codes
H-- Your boiler is simply indicating that there are currently no routine service reminders or maintenance messages to display.
Your boiler is simply indicating that there are currently no routine service reminders or maintenance messages to display.
What to check first
- No action is required as this is a normal status message rather than an actual fault.
H03 Your boiler is simply reminding you that it is time for its annual safety service to ensure it continues running efficiently and safely.
Your boiler is simply reminding you that it is time for its annual safety service to ensure it continues running efficiently and safely.
H08 Your boiler has reached its programmed service interval and is kindly reminding you that it is time for a routine professional safety check.
Your boiler has reached its programmed service interval and is kindly reminding you that it is time for a routine professional safety check.
H09 Your boiler has lost its electrical connection to the water pump, meaning it cannot circulate heat around your home.
Your boiler has lost its electrical connection to the water pump, meaning it cannot circulate heat around your home.
Parts commonly replaced
- Pump cable harness
- Printed Circuit Board (PCB)
- Central heating pump
Related codes
H12 Your boiler is having trouble reading the temperature of your hot water cylinder, which means it may temporarily stop heating your water properly.
Your boiler is having trouble reading the temperature of your hot water cylinder, which means it may temporarily stop heating your water properly.
Parts commonly replaced
- Cylinder temperature sensor
- NTC thermistor
Related codes
H13 Your boiler is simply reminding you that its scheduled service interval has passed or it needs its service indicator reset.
Your boiler is simply reminding you that its scheduled service interval has passed or it needs its service indicator reset.
Related codes
H29 Your boiler has lost communication with the weather sensor outside your home, meaning it cannot automatically adjust its temperature based on outdoor conditions.
Your boiler has lost communication with the weather sensor outside your home, meaning it cannot automatically adjust its temperature based on outdoor conditions.
Parts commonly replaced
- Outdoor weather sensor
- Wiring harness
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