Fault detection and isolation in automotive wiring harness

An automotive electrical system comprising, a plurality of electrical components (21,22,23) including at least one termination device, a wiring harness system interconnecting said electrical components and including a plurality of harness conductors (28) and a plurality of connectors (26), one of said connectors being a termination connector (26-1) connected to said termination device (21), said wiring harness system including a dedicated test line (55) provided by a termination conductor disposed in said termination connector and provided by more than one of said harness conductors, said dedicated test line (55) including a test point (56), electrical source means connected to said test point (56) for applying a test signal to said dedicated test line at said test point (56), and measuring means connected to said test point (56) for sensing a response of said dedicated test line (55) during application of said test signal.