Error code
Worcester Bosch Boiler E9 — Code Meaning
The manual assigns several E9 cause codes to different temperature limits and sensor conditions. The complete cause code must be read before diagnosis. Only for Greenstar 27i/30i System Compact ErP models in manual 6720813280 (2015/07), pages 63 and 70–71. Record the letter code and three-digit cause code together.
Quick answer
E9: Temperature safety or related protection fault; cause code required
Meaning
Temperature safety or related protection fault; cause code required
First safe check
Photograph the full display, including alternating characters and suffixes.
Stop if
The warning remains, the appliance is not operating normally, or the next step requires internal access.
Who to call
Contact a Gas Safe registered engineer qualified for this boiler if the warning remains, the code is not explained in the matching manual, or any internal investigation is required.
Internal diagnosis and repair require a qualified professional. Follow only the model-approved user actions described below. Keep checks outside the casing and use only a manufacturer-approved reset where the manual allows it.
What does this error code mean?
The manual assigns several E9 cause codes to different temperature limits and sensor conditions. The complete cause code must be read before diagnosis.
Only for Greenstar 27i/30i System Compact ErP models in manual 6720813280 (2015/07), pages 63 and 70–71. Record the letter code and three-digit cause code together.
The reported condition does not, by itself, establish which part needs replacement.
Why is this happening?
- The manufacturer describes: temperature safety or related protection fault; cause code required. The underlying cause requires assessment on the actual model.
Safe next steps
- Photograph the full display, including alternating characters and suffixes.
- Record the full model from accessible paperwork or an external label; do not dismantle the appliance to find it.
- Match the source below to your exact model manual before following any code-specific instructions.
- If the warning persists, the model is uncertain or the next step requires internal access, stop and contact a Gas Safe registered engineer qualified for this boiler.
Can I fix this myself?
NoUse only the external checks described here. The code alone does not justify a parts replacement.
Safety boundary: Do not remove the boiler casing or work on gas, flue components, combustion settings or internal wiring.
What not to do
- Do not remove the boiler casing or work on gas, flue components, combustion settings or internal wiring.
- Do not repeatedly reset an unexplained or returning warning, or buy parts solely from this display.
When to call a heating professional
Contact a Gas Safe registered engineer qualified for this boiler if the warning remains, the code is not explained in the matching manual, or any internal investigation is required.
Safety warning
Do not remove the boiler casing or work on gas, flue components, combustion settings or internal wiring.
Useful hub links
Other Worcester Bosch boiler codes
Worcester Bosch Boiler 224 — Meaning and Safe Advice
Flue-gas or heat-exchanger temperature limiter activated
Worcester Bosch Boiler 229 — Meaning and Safe Advice
Flame failed during burner operation
Worcester Bosch Boiler C6 — Code Meaning
Fan speed too high (215) or too low (216)
Worcester Bosch Boiler D1 — Code Meaning
Return sensor or return-temperature fault; cause code required
Relevant guide
Frequently asked questions
Does E9 identify a failed part?+
No. A code describes a reported condition, and the correct model documentation is needed before diagnosis.
Does this apply to every model?+
Only for Greenstar 27i/30i System Compact ErP models in manual 6720813280 (2015/07), pages 63 and 70–71. Record the letter code and three-digit cause code together.
Sources and review status
Model dependent · Last reviewed 21 September 2026
- Worcester Greenstar i System Compact ErP manual 6720813280
model manual · UK · checked 21 September 2026
Temperature safety or related protection fault; cause code required. Only for Greenstar 27i/30i System Compact ErP models in manual 6720813280 (2015/07), pages 63 and 70–71. Record the letter code and three-digit cause code together.