Do you have a Factory Service Manual with wiring diagrams to know what each wire is hooked up to?

 

Pull the tank and check the wires, if the bike is 20 years old,maybe one of them broke...the wires break at the point the connectors are crimped on , Dont be afraid to solder the new connector on, and crimp connectors work also. Could be a loose connector or ground, the vibrations work bolts loose. previous posters are correct about the multimeter, but start with a visual inspection, the multimeter would be used to isolate what wires are actually open/shorted. think of it this way...do you need to know exaltly what wire is effed up? or see that it is broke, reconnect it, the bike runs you are on your way. start with the simple things first. Dont tear the whole bike down if you dont have to...