@shadetree is 100% correct! As you now understand that voltage exists and current flows through every conductor in a functional circuit, including the frame. You can measure those voltages and currents using your multimeter, or confirm them with a test light. 

No, you were correct, you were testing the gear position switch for continuity to ground. Until you turned the key on that is..... at that point battery current flowed through your measuring device which terminated that measurement.     Yes there is.... in a functional DC circuit loop battery current flows from the positive plates in the battery until that current reaches the negative plates in the battery. Along the conductor path from those battery positive plates to battery negative plates current must pass through all of the wiring and circuit control components (which includes the gear position switch in this case) and the steel frame of the ATV. If any of those conductors fail the circuit loop is opened and current ceases to flow.     I think what many times confuses folks when it comes to understanding DC electrical circuits is that we tend to mix "Battery Negative" with "Frame Ground".... our minds assume that frame grounds are the end of the conductor path.... where in fact the ATV frame functions the same as any other "wire" in a closed DC circuit, since the Negative battery cable is attached to it.       "All it does is provide a path to battery negative" Fixed it for ya..... you're right about everything here, but fundamentally your understanding is flawed (which leads to making more mistakes inevitably), so I'm nitpicking ya a bit in fun.      The path to "ground" (Negative battery plates) did not disappear when you turned the key on, as evidenced by the Neutral light illuminating and other circuit indicators. What happened when you turned the key on is that you introduced DC battery current flow -- which flowed through the gear position switch into your measuring device, which caused your measuring device (multimeter) to cease functioning, as explained in an earlier post. The circuit worked fine, your multimeter got nuked though, which fooled you into thinking something bad had happened to the circuit.     It could be.... have you unbolted the negative battery cable from the motor and shined up the cable end and the aluminum where it bolts down? Have you removed and cleaned the ground cable that connects the motor to the frame? Have you removed and cleaned all of the wiring harness grounds that connect to the frame? Have you cleaned the coil and frame where the coil bolts to the frame?   I may sound like I'm picking on you but I'm not... and perhaps you've done the work already so I need to explain...... physically cleaning up all battery and negative ground connections should be done immediately after checking the fuses in dead circuits. It's the most important step in troubleshooting that folks must perform in my opinion, because I've learned through experience that a high percentage of ATV electrical failures are/were caused by poor battery cable connections and/or poor negative grounds. Poor grounds can even cause sensitive electronics to overheat and go up in smoke. So if you were to read the threads where I try to help folks find electrical issues you'll see me insisting that folks do all of the so called "ground" work first. We can't diagnose and fix anything until that work is done and when folks say "they look clean and tight to me" I say that doesn't mean they are all clean and tight.    We aren't electrical engineers here but I believe you're doing a pretty good job so far.   I gotta study a bit today then I'll come back to help ya.... I'm elbows deep in a project and all of my spring maintenance stuff is being held up by that work, so thanks for being patient.

Unfortunately that is 100% incorrect. There are seven wires to this switch, one for each gear, 1-5 and one for reverse, one for neutral. By your theory, every one of these wires should be hot. None of them are. This switch takes each circuit to ground when a gear is changed. Look at the OEM service manual wiring diagram for a TRX500FPM, this switch provides ground for the circuit. It takes each position to engine ground. There is absolutely NO power to the switch.

all honda's...including yours: the neutral light on the dash is ALWAYS hot at the switch, why ?, simple...the green/red wire leading to gear position switch is hot when key is on, when the light on the dash goes off when you change gears ?, this operation UNGROUNDS the light on the dash, herby at the gear position switch is no longer grounded with 12 volts, then the light on the dash turns off. when you shift back to neutral?, this again grounds the switch, which then makes the light on the dash light back up. confussing i know ?..but honda has done this for decades on all their atvs from day one. bottom line : gear position switch is ALWAYS HOT WHEN KEY IS TURNED ON. if your green/red wire leading to gear position switch does not have 12 volts going to it when you turn the key on ?, you need to find out why it does not ?. some atvs have what is called a diode plugged into the harness, see if you can locate this diode on your harness ?.

I think I misspoke in my video. Continuity wasn’t the terminology I was looking for. That gear position switch isn’t hot, there is never power to it. All it does is provide a ground to the appropriate wire that goes to the ECU, and the display on the dash. In essence, I was trying to determine that it was indeed providing that ground, which I should have realized it was, since it displays properly on the dash. So what I was doing was confirming that the green/red wire was indeed grounding as it should…..until I turned the key on. Why would the ground disappear? And since the coil is grounded to the frame, like the green/red wire in my test, is it losing ground when I turn the key on?