it means ignition lockout and will indicate faults with electrodes, gas valve, condensate blockage, pcb, ignition transformer, gas supply fault and incorrect co2 ratios. if you can re-set without it happening again then it should be fine, otherwise it's a job for an engineer.
the only thing you can check yourself is that the condensate pipe isn't blocked or frozen.
most common fault i've come across is incorrect co2 ratios, which causes the electrode to bend, in this case it needs new electrode an co2 ratios re-set.
Ian, April 2010
