Control panel saying I’m on hook up?

Just spent the night at a pub stopover in the New Forrest & when I’ve just started up & pulled away I got a high pitched alarm sound, pulled over & checked the rear to find the control panel warning me that my engine is running whilst I’m plugged in? Clearly I wasn’t plugged in as we had no electric, why would the panel give this warning? 

It’s fine now… I hadn’t powered down the control panel before moving off so that may have triggered it, don’t usually worry as everything goes off when you start the engine, only thing I can think of, just hadn’t happened previously, having said this I’m still getting used to things.

On mine before disconnecting from the EHU I turn the Truma heating and hot water OFF and then turn the Truma CP OFF.  I then turn everything off on the EC700 CP including its Power Button but not the EC700 PSU under the seat.  I once started the engine whilst still connected to an EHU to read the wretched LPG gauge and had all the alarms you have experienced.  I cleared it eventually by shutting down the EC700 PSU which as Dbvwt has said is a bit like shutting down a computer to clear a fault. Has the P 948 whatever that means cleared from the Truma CP?