A vehicle electrical system tester for testing the electrical system of a vehicle is provided. The electrical system has a wiring harness which extends between components of the vehicle and includes a plurality of wires. The vehicle electrical system tester is configured to measure an electrical parameter of at least one of the plurality of wires through a first connection to coupled to a first end of the at least one of the plurality of wires and a second connection coupled to a second end of the at least one of the plurality of wires. An electrical signal is applied between the first and second ends of the at least one of the plurality of wires and the electrical parameter of the at least one of the plurality of wires is responsively measured.