ATAG · iC, iS and iR range
3P9Scheduled maintenance due
This code applies to iC Economiser, iC Combination, iS System, iR Regular. Fault codes narrow down the likely problem, but they do not replace a model-specific diagnosis.
What you can safely check
- Do not remove the boiler case.
- Record the full code and model, then arrange a Gas Safe registered engineer.
How an engineer may fix it
Follow the model-specific fault-finding procedure, test the indicated circuit or component, repair the cause and recommission the appliance.
Manufacturer source: ATAG — Boiler Troubleshooting (2019 & newer i-range). Checked 15 August 2026. The appliance manual and an engineer’s on-site diagnosis take precedence. Never remove the boiler case yourself.