I don't remember exactly how this worked, but another member previously mentioned this unorthodox method in a similar thread:I have never done this, nor do I plan to ever do it
Disconnect a spark plug wire from the truck (w/ engine off
Run a jumper to the UG wire (be sure to disconnect all the other connections to the UG wiring)
Start truck, and walk along with an AM radio that's tuned off of any channels. The "ticking" will be picked up by the radio, and will be louder the closer you get to the UG wire.