have you done anything to the vehicle recently or right b4 this happened if yes start there, if no get your wiring diagrams out and check your getting earths and live feeds in the correct places, start at the battery and work through the electric system making sure you have the right voltages( battery-ign switch-ign relay-etc,etc)or you can just jump straight in and start at the ecu multiplug but you might miss something doing this. good luck