Problem with Vaillant ecoTEC plus 624

I have a problem with a Vaillant ecoTEC plus 624. For the last week we've only had hot water when the heating is on. There are no fault codes - only status codes (S.4, S.6, s.8 and S.31). The tank is a MEGAflo, not sure of the model but can find out if it's important.

In a previous post on this site someone asked about the same problem with a Turbo max VUW 242-1E Combi boiler. The answer was:

"Check operation of electrical switch (black plastic housing) on side of diverter valve (bottom right front corner of appliance). If arm is not moving far enough to activate switch, adjustment can be altered."

Could this be the same problem with the ecoTEC plus 624? If so, does the same thing apply and is this something that I can check or should I get someone in?

Many Thanks

No it won't be the same problem. The turbomax was a combi and yours is a system boiler.

You need to check your 2 port ch valve. There appears to be a fault with this and not with your boiler.

Sorry for my ignorance.... where is the 2 port ch valve and what should I check for?

Thanks