Error code EA 258 on Worcester Greenstar compact 25i boiler?

Got in on New Year's day after a day at work and my partner said heating had been off most of the day and no hot water- was surprised as it was a complete new heating system to replace the old gas-fired warm air heating system.
On checking the boiler there was an EH or is it EA code 258 (internal error code) What is this? I phoned Bosch but of course they are closed for the holidays. I reset the boiler and it restarted. Not been able to find any info about this error code. Can anybody help?

Boz
January 2015