I need HELP! Having issues with my 07 FX2. Last week the left brake light/turn signal quit working. All other lights worked at that time (see where I'm going with this?). So, easy fix right? Bought a bulb at Oreillys and replaced. Did not fix the problem. Okay, so Christmas, work, etc. Then the other day the right side brake light/turn signal quit. Huh? So I've done the internet research and read of the Multi Function Switch problems, etc. The only anything not working on truck are these 2 lamps. So for fun I went and bought 2 more bulbs and replaced. I first replaced the right side brake light, and it fixed it! Then replaced the left side, no change. BUT, get this; after replacing the left side, the right side quit working but the tailight lamp is now working as the brakelight/tailight/turn signal???? How is that possible? I never touched a thing except the bulbs.
So to recap:
Left and right side brake lights do not light up at all.
Right taillight is now working as brake/turn/tail lamp.
All other lights and accessories on vehicle work fine.

Tactics I have tried:
Replaced bulbs twice
Tried the wd40 on the hazard switch
Cleaned all connections at the bulb and socket connections
Cleaned connections on and to Multi function switch

Please Help!! and thanks in advance

 

Pull fuses # 36 & #42 and retest.

When you test try both the turn signal for each side, as well as the hazards.

The thought is the trailer tow adapter is crapped up and this might be causing an issue with the truck.

the 04-08 MY trucks do not have the relay isolating the Stop / turn signals on the Trailer tow adapter and the truck's stop / turn signals.

 

I will try it! Thanks for the info.

 

I tried your suggestion but still no change. Still have the drivers side brake light/turn signal not working at all and the passenger side brake/turn signal is working through the taillight....

 

Was hoping this was an easy one.

With the trailer tow fuses out, it sounds as if one side does not have a ground.

Pull the tail lights and check with a meter from the Stop / turn to an external ground to see if you have + VDC when the turn signals or brake is on.
- You want to check not only to the bulb holder, but also to the wire 12" back from the bulb holder with an ice pick or test light that will pierce the insulation.
Fluke has some mice clips, don't know if you can find them local or a brand x version, these can be somewhat expensive ( fluke TP-81 ). I found them worth the money in the time saved.


if so, check the same with the ground on the parking lamp.

Sounds like a bulb holder could be corroded and causing the problem on the other side.

 

Thank you, I will give it a try and see!

 

signal for each side, as well as the hazards.