ATAG · iC, iS and iR range
1P1Flow check 1 failed
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
- Check the system pressure and make sure accessible radiator valves are open.
- Allow an overheated boiler to cool and reset once only if the user manual permits it.
- If the fault returns, stop resetting and arrange an engineer.
How an engineer may fix it
Diagnose water circulation, air locks, pump operation, valves, bypass, blockages, heat exchanger and temperature sensors; restore correct flow and test the safety controls.
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.