I've tried using this a few times, my V90 has a genuine Volvo tow bar and electrics. I connect the caravan/trailer with the ignition off, get in the car and turn the ignition on and get the message below, but whatever I press I cannot get the function to start. None of the steering wheel buttons move the cursor up to highlight "check the lamps". I can't find any information in the manual on how to use this function, anyone know?