Single red wire coming of out heatshield by starter?
 

I'm still learning new things about this trucks and this one kinda has me stumped.

It's a single red/pink wire that comes out of the heatshield for the starter wiring and jumps over to the frame. It then goes back towards the rear and right near the end of the cab/fuel selector valve it seems to have a single connector (pictured). It then appears to enter a taped loom and head across a crossmember with some other wiring and heads back towards the front of the cab.

What's going on here?

Here's a couple pics:

http://i.imgur.com/YNrii4L.jpg

http://i.imgur.com/TIpUrXS.jpg

Re: Single red wire coming of out heatshield by starter?
 

That is the wire foe the gas gauge.

Re: Single red wire coming of out heatshield by starter?
 

I checked and you are correct. What an odd way to route it.