Q: the vehicle is an ex-UK. 1997 MODEL.D8.with coded key pad.two ignition coils have been replaced.the fault developed after the engine overheated.
A: Maybe your alternator is overcharging? get a multimeter and check the voltage while running. check the voltage supplied to the coils (probe the supply to the primary windings) in case the electrics are damaged and oversupplying. did the replacement coils blow? could be just dud coils. The originals would have suffered thermal damage from the overheat.