Vehicle has been on the diagnostics computer apparently its a bad earth somewhere.could this bad earth have anything too do with my stereo system ,amplifiers and woofers if one of these lost their earth through a loose connection could this effect whether the car starts or not.before the car packed up it was juddering over the road loss of power like a fuel problem it is a diesel (nightmare).and its recently had another fuel pump fitted and fuel filter.2 months ago.please can you help. many thanks