This is an example of why test lights are misleading. Meters are only $1.99 on Harbor Freight when they're on sale, and only $5 otherwise. The orange wire with power is a serial data communication wire that goes all around the vehicle and lets the modules talk. It would have a fast digital signal on it - sometimes high and sometimes low, and a meter would average it out and give you some reading like 5 or 7 volts. If you put the meter on the AC scale it would have some significant reading like 3 or 5 volts. On a true battery power wire, it would read 12V on DC, and 0 v on AC. Your test light is probably a bit dimmer when looking at the data communication line than it is looking at a battery power wire. But the slight change in intensity is hard to see. With a meter it's instantly obvious.
Anyway, the lower wire should have battery power and you have a wiring problem or a blown rear fuse #41. Meters are also better for testing fuses than a test light, since you can test for continuity on a resistance scale when it's not plugged in.