Need Help Replacing '08 Q7 Tail Light Harness
 

My '08 Q7 has had a variety of issues since I picked it up 2 years ago. I noticed that a tail light was out, so I went to my local dealership and they gave me a free bulb. I went to pull out the old bulb and the 'bulb' portion came out, but not the metal casing (i.e., the bottom half). It was stuck in the plug. I finally got it out, but unfortunately it disconnected the plug from the black wire. After tinkering with trying to reconnect the wire for 10 mins, I got frustrated and decided that a service tech at the delearship could just quickly do it for me. It turns out that I'm wrong.

They said that they need to replace the harness ($80) + $250 labor. An indie shop charges $150 labor. Anybody have experience with this type of problem? I'd hate to spend a few $100s when I was simply trying to replace a bulb. Do I really need to replace the harness or could I splice the wire, use some electrical tape and call it good?

The part number for the harness is 4L0-945-221-B


https://cimg0.ibsrv.net/gimg/www.aud...6a4f64e827.jpg


Black wire disconnected from prong


https://cimg3.ibsrv.net/gimg/www.aud...d9344dca05.jpg


You can see that the prong is missing and the black wire isn't connected.


https://cimg4.ibsrv.net/gimg/www.aud...9a4fce8322.jpg


I still have the prong and old casing

The Q7 needs good volts from the light bulb to turn off your control mode error code. Your 2008 is old and the harness is old. I recommend to replace the harness and save the headache in the future.

Will look up the procedures

need to removed the trim panel, harness will be visible.

I picked up the 2 harnesses and 6 new bulbs at the dealership. With the 25% coupon, it was only around $100 + tax. It took me probably 90 minutes to do the entire thing. Having no visual guide, I thought that was a reasonable amount of time. Taking the trim off the was most challenging part because I really didn't have any idea how the tailgate trim was held in place. Other than a number of screws, it had steel suspension springs that you just had to pull down on. I had the tailgate trim halfway off and was able to find the 3rd screw keeping the lights in place, so I actually did all the work with the trim only partially removed.

When I tried putting the trim back on, I realized I couldn't do it unless I took the other trim pieces off. That's when I was lucky enough to find this video, which gave me a general idea of how to remove the trim: .

I needed my wife's help to put the main piece of tailgate trim back on. It is a bit worrisome to think that it's only supported by 2 wires once you remove all the screws. I recommend having a 2nd set of hands to help put that back on. It only took a few minutes.

If you're interested in seeing the harness before I replace it, here's a photo.

https://cimg0.ibsrv.net/gimg/www.aud...474168af64.jpg

Driver side tail light harness

So I was search through threads trying to find a guide to remove the tailgate trim to remove the tail lights and swap out the wiring harnesses since I was getting a bulb failure every few weeks because of the failing old harness. I came across this thread which helped but still didn't give me a complete picture of what I needed to do since the tailgate trim video in the above link isn't specific to the Q7. I then came across this youtube video that told me about the torx screw behind the cover in the sunscreen clip at the top of the tailgate.


Hope this helps someone who hasn't had to swap the tail light wiring harness yet.

Having mine replaced today. I keep getting a brake light out warning on the dash so I asked my mechanic to check the bulb while my car was in the shop for carbon related issues. He checked the bulb and sent me a picture of the harness.... totally fried socket.
The computer requires a certain amount of signal communication back from the bulb in order for that dash warning to clear. With the socket being totally cooked it wasn’t getting the correct voltage.
Quoted $77 bucks installed and I’ll be good to go.

I would recommend doing both the left and right side harnesses at the same time since the labor is mostly to remove the trim panel. once that is off, it's fairly easy to swap out the harnesses, and if one harness is starting to die, the other isn't far behind. When worn, the bulb plug sockets don't maintain good contacts with the bulb, despite rebending and cleaning the contacts. Much better to swap out for new ones on both sides.

So far I had my mechanic replace the one harness but now I’ve got more issues. The brake lamp warning is gone on the dash which is great but now when I use my turn signals strange things happen. Turning left all signal lamps work but now turning right the lamps on the right side of the lift gate don’t work but the rear bumper signal flasher does. Wtf...

Just received my new taillights today for my 07' Q7. My old ones melted to the bad wiring harnesses. I ordered them from autohausaz.com along with 2 new wiring harnesses. The taillights that came are Magneti Marelli. I don't know if that is the OEM manufacturer, but they come with a wiring harness already installed. So now I have 2 extra wiring harnesses. No biggie, nice to have in case the new harnesses fail again.

Thanks for the video above about how to remove the trim from the hatch. That makes my job alot easier. Let there be light, and no tickets for having no working taillights 😉

Edit: Apparently the current to the bulbs is not sufficient to power the Phillips ultinon led 1156 bulbs i bought. Have to go to the store and see if regular incandescent 1156's work. ...and the incandescent work, hallelujah 🙌

Are the extra harnesses two of 4L0945221B (#5 in diagram)? At $78.99 each I would just return them for refund for now. I think the original factory harnesses had defects, and you should not have problems with the new ones that came with the lamp housings.

I did not look at who made the lamp housing. On my 3.6L, Magneti Marelli also makes the fuel injectors, powered by a Hitachi high pressure fuel pump.

https://www.autohausaz.com/pn/VW-4L0945221B

https://www.autohausaz.com/ez-parts-returns

Yeah, they're the oem harnesses #5. I am going to return them. Upon second inspection of the old lights, they were Magneti Marelli. Thanks for the return link.