Day by day customer's demands on vehicle features and functionalities are increasing which results in complex wiring harness systems. This in turn requires robust protection in the circuits to ensure proper working as well as avoid malfunction or damage to wiring system during short circuit or over current scenarios in the vehicle.Short circuit test gives you assurance of wire capacity to withstand high current till the fuse blow. If fuse don't blow within specified time as per selection of fuse, it is essential to check wire size as well as fuse rating.This paper gives details of short circuit and over load test of circuits to verify its performance. The methodology involves the compliance to S.C test criteria at every stage of development through simulation, bench testing & vehicle level validation. The various acceptance criteria's includes requirements like no damage, melting or smoke from Wiring Harness, wire insulation shall not exceed maximum operating temperature specified for wires, no thermal/fire incidence on the vehicle under short circuit or overload phenomenon.Considering the simulation results & vehicle architecture we can find out required wire size, wire type and fuse rating. The validation can then be done on vehicle. This Co-relation between simulation & validation in turn helps in more accurate prediction & reduces development time considerably.The methodology was evolved and implemented on TATA MOTORS Aria Car. The same methodology is being implemented in the new models under development.