I had meant to write some pieces on sporadic faults but I had not got round to it. Be careful with these types of faults as they can be very misleading. Along with other faults it can just mean your battery is low. All of these can show up as individual faults on the diagnosis readout and lead one to believe everything on the vehicle is going haywire. Other symptoms are the sat/nav screen is blank and the route may not show, other things go into shutdown 'graceful degradation' one by one. I have had this happen on a number of occasions when the battery is low.
