The tail light issue is usually a burnt plug in the tail light housing that is for the brake and tail. As for the fuel gauge I don't believe they are on the same circuit. I know my 04 flhsci would blow the accessory fuse I'd lose brake lights and the speedo and dash would go dead. Never did find that wire that caused it it just stopped blowing fuses lol

 

Thanks for your reply. I checked the wiring, connections & fuses & everything "looks" ok. When I reconnected everything the tail light worked for a minute but quit again. I'm at a loss at the moment but will check continuity between the connector under the seat & the one at the light housing to condemn or eliminate the harness.

 

A quick look at the wiring diagram looks like the running light power output from the BCM powers the fuel gauge so they are connected.

As your bike has a BCM it controls the power to devices and has current limit protection so no fuse.

I am guessing that when you turn on the ignition whatever is the fault builds after the short time interval and the BCM cuts the power.

Check for codes - Harley Trouble Codes (fuelmotousa.com)

wiring diagram - 99949-16_en - 2016 Wiring Diagrams (harley-davidson.com)

 

Thanks for your reply. BCM issues suck. We had some of those on two Saturn cars. Inconvenient & expensive. Still wondering if it could be the harness that goes from under the seat, under the rear fender & into the tail light housing. I'm getting 12v at the male connector under the seat. Not getting any voltage at the tail light. The brake light & turn signals still work.

 

Trial and error. If you unplug the tail light does the fuel gauge work and what if you just disconnect the fuel gauge?

Process of elimination.

 

Unplugging the tail light at the light housing didn't change anything w/ the fuel gauge. I'll disconnect the harness under the seat & see what that does...