So I got a lovely new tow bar fitted with the dedicated electrics all well until I put the caravan on the back then I get a warning triangle on the dash and the infotainment tells me to check my numberplate light - I did and they were all working. now as it happens the caravan only has one numberplate light whilst the car has two - could this be the issue?

Is this something that can be coded out?

having the tow bar and putting a caravan on then getting the warning might simply be a coincidence .I have the exact  same thing happen occasionally with my estate ( no towbar ) on checking both number plate lights are working, simply switching ignition off and back on puts the warning out.