How is a voltage drop test performed across a suspected high-resistance electrical cable or connection?

1. By connecting a voltmeter in parallel with the suspect component or cable while the circuit is active and under load
2. By disconnecting both ends of the cable and measuring resistance with an ohmmeter
3. By checking for continuity between the cable and the engine ground with the key off
4. By measuring the temperature of the wire with an infrared thermometer while inactive