An apparatus and a method are provided for a wiring harness configured for a compressed natural gas (CNG) powered vehicle. The wiring harness comprises an assembly of wires to convey electrical signals. The wires may be bound together by straps, cable ties, cable lacing, sleeves, electrical tape, conduit, a weave of extruded string, or a combination thereof. An exterior sleeve comprises a protective over-molding for the wires. The exterior sleeve seals substantially all connections between the wires and connector terminals of the wiring harness. The exterior sleeve may be flame-retardant and configured to withstand extreme weather conditions. A regulator controls expansion of high pressure CNG to a lower pressure gas that may be utilized in the CNG-powered vehicle. An integrated kill switch prevents engine starting during fueling. The integrated kill switch prohibits engine starting when a fill nozzle cap is improperly installed onto a fill receptacle.