Project E46 M3 - Replacing LED Taillights July 29 2021
Our BMW E46 M3 had a rear turn signal go out. However, instead of being able to simply swap in a new bulb, our M3 is a late model (2003+) with the LED taillight assembly. The taillight assembly is a sealed unit and the LEDs are not intended to be replaceable. Moreover, LEDs are quite robust and it is more likely that a board inside has malfunctioned, making diagnosis and repair harder than simply replacing some LEDs. Short of opening up the taillight assembly and performing some surgery, replacing the entire taillight assembly is what you'll have to do. Follow along to see how it's done.
Part numbers for late model coupes are shown below, but will be different for sedans, convertibles, early models, etc. Verify your part numbers on a website like realoem.com .
LED taillight with amber turn signals, left: 63216937449
LED taillight with amber turn signals, right: 63216937450
LED taillight with white turn signals, left: 63216920699
LED taillight with white turn signals, right: 63216920700
Trim piece, left: 63216933017
Trim piece, right: 63216933018
Open the trunk and remove the cover on the forward side of the taillight. You simply pinch the tabs together and the cover comes off.
Undo the electrical connector by pinching the release tabs and then pulling the connector out.
Loosen the 3 nuts holding the taillight assembly onto the chassis. You'll have to pull back the trunk liner a little to gain access. We used an open ended wrench, as a socket doesn't have room to maneuver.
The taillight can now be removed by pulling aft on it.
Before you just swap in a somewhat expensive taillight unit, verify that it is an issue with the taillight assembly and not the harness or anything else upstream. The harness connectors on the left hand side and right hand side of the car are the same. We swapped the right-hand taillight (which is know is good) onto the left-hand taillight harness, and it worked fine. This tells us that the issue is with the left-hand taillight assembly and not with the harness or anything upstream.
For extra confirmation, we plugged the left-hand taillight assembly into the right-hand harness and the turn signal still didn't work. This provides additional confirmation that the left-hand taillight assembly is what is broken.
The new taillight assembly does not come with the inboard trim piece. You can either reuse your old one or get a new one. We recommend just getting a new one because it is difficult to remove the trim piece. Additionally, the rubber seal on our trim piece had a slight tear and had also detached. We didn't want to bother with gluing it.
Nonetheless, if you want to reuse your trim piece, this is one way to remove it. There are a bunch of locking tabs holding the trim piece on, and it's hard to get them all unlocked at the same time.
Some bamboo skewers and toothpicks were able to hold a few of these tabs open. Note that the trim piece is made of ABS plastic, which is quite tough and bendy, while the taillight assembly is made of a harder plastic which is more brittle. Move the bendy trim piece tabs and not the taillight tabs.
Then, while providing a constant separating force, we went from one end to the other, prying open the tabs with a flathead screwdriver. The separating force allowed the tabs to stay unlocked once they were unlocked. This is similar in concept to picking a lock, if you are familiar with that technique.
Once the trim piece is off the old taillight assembly, simply pop it onto your new taillight assembly. Reinstallation of your taillight assembly is the reverse of removal.
You now have functional taillights again!