Objective: How to find a bad wire in a car.

Which of the following solutions is more sound in terms of naive physics reasoning?

Available choices: (A). Locate the radiator its metal box, run your hands through the wires with the car off and gently wiggle them, if you see a spark its possibly grounded to metal and a bad wire.. (B). Locate the ECU its plastic box, run your hands through the wires with the car off and gently wiggle them, if you see a spark its possibly grounded to metal and a bad wire..
(B).