[brian22308]

My F22 drivers side tail light is giving me problems. Brake, turn signal and reverse all work fine, but tail light does not (the rear lights that come on with the headlights).

Ground fault was fixed a couple years ago, and ground tests fine on the multimeter at the harness and on the light board.

Do the tail lights illuminate from the same bulbs as brake, at lower voltage?

Anyone know which wire harness pin supplies this function? Or is it lower voltage through the Brake light wires?

This all started after a bad seal let the light get a bunch of water in it.

[brian22308]

Should also add that there are no faults reported on the dash.

[TrboMike]

If water got in, theres a high chance you have rust somewhere like on bulb socket. There are no wires inside just metal traces to carry the current. One of those could also be rusted/broken.

You are pre LCI so you have the older tailight? I forget how many parking light bulbs there are, are they ALL out or just one? I'm surprised you dont have an error in Idrive.

I'd remove the whole tail and open it and see whats doing on inside.

[brian22308]

Yes, it was definitely corroded inside. I cleaned it all up, including all the bulb contacts and replaced bulbs. What's strange is all the bulbs work for some functions, do not illuminate for just tail lights . So, they come on for brakes, signals and reverse lighting, but do not light up for the tail lights. I'm assuming the tail lights illuminate from the same pins as brake and reverse but at lower voltage, but not sure.

[Coupsoup]

Tail lamps and brake lamps will have separate circuits that both use 12v.

You want to check for power on the Grey/Violet wire pin 2 and Yellow/Black wire pin 5

[jzeiler4]

Having a bad ground can cause all the lights to light up as they feedback to the other bulbs looking for that missing ground.

[Verloren]

I have the same issue with water getting in through the harness, but also the red lens has come unstuck. are there aftermarket options that are better made?

[Coupsoup]

Originally Posted by jzeiler4

Having a bad ground can cause all the lights to light up as they feedback to the other bulbs looking for that missing ground.

His tail lights are LEDs, this is not a thing that can happen with LED.

[jzeiler4]

Originally Posted by Coupsoup

His tail lights are LEDs, this is not a thing that can happen with LED.

Actually the OP stated bulbs in his post. He is pre LCI. Your diagram shows bulbs as well as a couple of LEDs

[Coupsoup]

He mentioned tail lights, the tail lights are LED according to the schematic.

[jzeiler4]

When you say "tailight" you mean the function, I think he means the entire assembly as the "tailight". But maybe I read it wrong. In fact I went back and read it again and MY Bad he did mean the function.

[brian22308]

I'm referring to the taillight function, as in the lights that are on when your headlights are on, not the entire assembly - very confusing, sorry about that. So after pulling it apart, I now see there is a contact that plugs from the bulb holder into the taillight assembly (what you might refer to as the lens). Those contacts are testing to 12v, so there is power to that plub. it would appear there is another bulb inside the taillight assembly. it's possible that is an LED. (others are bulbs on the 2015). No continuity from the plug on the assembly, so likely a burnt bulb or led. will try and open that up and report back.

[brian22308]

yes indeed, there an LED of some sort, and it's not working. Look like a new tail light assembly. Might be worth a visit to the dealer to see if they have any unadvertised campaign for this goofy design, but not likely at this age.

[Coupsoup]

Originally Posted by brian22308

No continuity from the plug on the assembly, so likely a burnt bulb or led. will try and open that up and report back.

LED's are light emitting diodes, that means that current only flows in one direction, which means if you're testing through it to ground for continuity it's going to be OL or extremely high resistance due to the solid state electronics on the board.

There are no open recalls related to the lighting systems, however there are two TSBs for the tail lights. You can pull the tsbs at nhtsa.gov, here are the numbers.

SI B63 05 17 - tail lamps inop, insufficiently grounded
SI B63 07 16 - water in the tail light assembly.