Method for detecting an isolation fault in an isolation resistance between a positive and negative high-voltage bus rail and a vehicle chassis on a high-voltage propulsion side of a high-voltage system of an electric or hybrid-electric vehicle, wherein the high-voltage system is split into a high-voltage battery side and the high-voltage propulsion side by means of first and second high-voltage contactors located in the positive and negative high-voltage bus rails , respectively, wherein the high-voltage propulsion side comprises a first and second capacitors connected in series across the positive and negative high-voltage bus rails , and wherein a common junction of the first and second capacitors is connected to the chassis, characterised in that the method comprises: ensuring that first and second high-voltage contactors are set in an open state, operating an isolated DC/DC converter for converting a supplied high-voltage from a high-voltage battery of the high-voltage battery side to a low-voltage output on the high-voltage propulsion side , supplying the low-voltage output to the positive and negative high-voltage bus rails for simultaneous charging of the first and second capacitors , registering a charging current, voltage level or energy level of the first and second capacitors , and determining, based in the registered charging current, voltage level or energy level of the first and second capacitors , whether an isolation fault between the positive and/or negative high-voltage bus rail and the vehicle chassis on the high-voltage propulsion side of the high-voltage system is present. wherein the high-voltage system is split into a high-voltage battery side and the high-voltage propulsion side by means of first and second high-voltage contactors located in the positive and negative high-voltage bus rails , respectively, wherein the high-voltage propulsion side comprises a first and second capacitors connected in series across the positive and negative high-voltage bus rails , and wherein a common junction of the first and second capacitors is connected to the chassis, characterised in that the method comprises: ensuring that first and second high-voltage contactors are set in an open state, operating an isolated DC/DC converter for converting a supplied high-voltage from a high-voltage battery of the high-voltage battery side to a low-voltage output on the high-voltage propulsion side , supplying the low-voltage output to the positive and negative high-voltage bus rails for simultaneous charging of the first and second capacitors , registering a charging current, voltage level or energy level of the first and second capacitors , and determining, based in the registered charging current, voltage level or energy level of the first and second capacitors , whether an isolation fault between the positive and/or negative high-voltage bus rail and the vehicle chassis on the high-voltage propulsion side of the high-voltage system is present. ensuring that first and second high-voltage contactors are set in an open state, operating an isolated DC/DC converter for converting a supplied high-voltage from a high-voltage battery of the high-voltage battery side to a low-voltage output on the high-voltage propulsion side , supplying the low-voltage output to the positive and negative high-voltage bus rails for simultaneous charging of the first and second capacitors , registering a charging current, voltage level or energy level of the first and second capacitors , and determining, based in the registered charging current, voltage level or energy level of the first and second capacitors , whether an isolation fault between the positive and/or negative high-voltage bus rail and the vehicle chassis on the high-voltage propulsion side of the high-voltage system is present. <EOS>