Truma combi 4e error e202h

[sako]

Truma combi 4e (2017). When using gas only I get an error message when I turn the heating temperature down on the control panel, the boiler makes a ‘click’ and the fans slow down. I then get an E 202 H. This error message will not clear and the entire system has to be turned off and restarted. I can then start the heating again on gas.
The gas pressure is normal and the boiler will operate with all the cooker burners lit as well as the fridge.
If I turn the control to electric or mixed when I am not connected to electric supply I get a W 45 H message which clears as soon as I switch back to gas only. In fact all error messages clear when the error is rectified except the 202 message.
I do not believe it is a gas pressure issue because the boiler works perfectly on gas until it shuts down so Is this a fault with the PCB in the boiler?

 

[Speve]

202 comes up as gas supply closed? I would think there is a valve that shuts when changing to electric?
45 is no230v operating voltage or 230 v fuse defective or overheating protection triggered

 

[sako]

My issue is that when I close down the heating from the control panel or adjust the temperature below the Internal temperature. Instead of just closing down the gas heating, I also get the 202 message after the gas valve has closed (clicked shut).