Car Wiring & Wiring Harnesses for Citroën for sale | eBay Citroen C4 Wiring harness adapter lead -. Citroen C4: 2004 onwards. It will convert the car's original wiring plug to a standard ISO connector which fits straight into your new stereo. This wiring harness will fit the following vehicles. 5 out of 5 stars. Citroen Wiring Harness Adapter, Radio Install Wire Harness Citroen headunit car audio wiring Harness Adaptors, ISO car wiring loom harness adaptors, ISO harness suitable for the following Vehicles. 0. Subtotal: Citroen C4 2005 Onwards Radio Wiring Harness + DIN Antenna Adaptor.