E168 Error ?

I have a Maxi combi Bolier installed 2008 over the past 2 months continual E168 error message .
After 6 engineer call outs from my Gas and Electic company and very patient Gas Engineers. Finally Baxi are willing to come out and look at it . Fingers crossed they come out and fix it. If i hadn't have the additional cover on my Gas and electric by now this would be costing me alot of money . what is the point having an Error message that could potentially mean 4 + different errors. confused.com !!!!!