This error code denotes absence of flame either due to ignition failure or the boiler not detecting the flame. This may be due to an ignition electrode or spark generator failure. Second, the detection electrode or detection lead may be faulty. Third, a problem might have occurred in the condensate pipe or condensate trap.
The simplest ways are:
- Check the condensate pipe for clogs or damage and repair/replace it if necessary
- Clean the ignition electrode and check the spark generator. Repair/replace these parts if necessary.