DIY for Rear Tail light Ground Short Problem
I recently experienced that annoying faulty ground wire issue on the rear tail light that SO many E46 owners are familiar with. I looked up the parts to fix my car and discovered that the BMW replacement wiring harness
patch is $570 and the bulb carrier is $42 totaling $612 in parts alone.
Since BMW has not accepted responsibility for this issue in the form of a re-call I decided to fix it my self using parts from Canadian Tire. Thought others might want to see a cheap way ($9.52) to fix their faulty rear tail lights.
First: Take the bulb carrier out and remove the wiring. You will see that there is damage to the number 3 wire (the brown ground wire). Using a wire cutting tool trim the number 3 probe on the bulb carrier so the ground stops shorting. Do not cut the brown ground wire. It is important to leave it untouched so if BMW ever does a recall on this issue the wiring is untouched and BMW will replace it for you.
Second: Remove the rear tail light lens. Use a razor blade and trim the tab off the lens as I showed on the photo labeled "lightbackfix.jpg".
Third: Cut a 15 inch length of wire (14 gauge wire) and crimp round closed wire ends on each end. Don't use small wires, that is the original problem!
Fourth: Using a short bolt and nut (make sure the bolt is not long enough to short onto the lower electrical plate) fasten one end of the wire to the top hole on the ground plate of the rear light carrier as shown in the photo labeled "lightfix.jpg".
Fifth: Tuck the wiring behind the shields in the trunk and attach the other end of your new wire to the negative terminal of the battery as shown in the photo labeled "batteryfix.jpg".
Six: Re-assemble everything and test to make sure everything is working. If you did this correctly your lights will work like original and the dash indicator will show your lights are fine.