negative starter wire and starter kill relay

2008 nissan alitma has a negative starter wire at the BCM behind the cluster. My question is whats the best method of testing for this wire? Also once it is cut for the start kill relay what is the best method to test for the key vs starter side? Thank you in advance for your help!! :)

Use a DMM, red probe to a constant 12V+, black probe to the wire, set DMM to 20VDC. You should get a momentary 12.5 Volts on start. Or ignition on, ground suspect wire through a 12V incandescant test light. Once established, cut wire, the side that goes to ground is your key side. Incidentally if you have to ask this question you shouldn't be doing this.

howie ll wrote: Use a DMM, red probe to a constant 12V+, black probe to the wire, set DMM to 20VDC. You should get a momentary 12.5 Volts on start. Or ignition on, ground suspect wire through a 12V incandescant test light. Once established, cut wire, the side that goes to ground is your key side. Incidentally if you have to ask this question you shouldn't be doing this.

thanks for the reply but thats not how this particular vehicle was. I am well aware of everything you just said. I was simply curious as to what other installers do. Your explanation of how you test for the key side is still a bit unclear. The 2008 Altima I was working on had a negative starter wire (tech info provided by directechs) that rested at 12 volts and when you started the vehicle it would drop voltage to 0.0 When cut the vehicle would not start.   Anybody else see this before??