DIY: Remove headlight control unit (cornering light malfunction)

[Oughourj]

Hi guys,

So recently I've been getting an intermittent 'right cornering light malfunction' on startup on my 2010 135i adaptive headlights, xenon. Weird thing is, when I checked the fault in the nav system, and clicked on the fault, the description would be 'left cornering light malfunction, please contact bmw etc.' Eventually the fault would appear more often and sometimes stay and sometimes clear itself while I drive. Even with the fault present, everything worked normally including the adaptive headlights.

I talked to a BMW technician and right away he knew the problem, he said I had to take out the headlight control unit, try cleaning the connections, and if that doesn't work then replace it ($380 online) AND that it needs to be programmed. It's part 14 on the realoem diagram, part no. 63117180050. Apparently moisture gets in there and fries the circuit board in that unit, but since mine was an intermittent fault I thought that cleaning might help and because of the right/left fault confusion, I just decided to clean both.

Disclaimer: I am not a certified mechanic. This DIY is solely an informative guide and I will not be held liable for any damage to your vehicle or harm done to yourself or anyone else while following these steps. I would not recommend following these steps if you cannot at a minimum SAFELY raise your vehicle with a jack and change a tire.

1. First things first, loosen lug nuts.

2. Raise vehicle with a jack. You can do one side at a time and use the forward side jack points, or raise the car from the front jack point.

3. Remove wheel and place under the car just in case. I would recommend using a jack stand of course. As always.. never get under a car that is solely supported by a jack.

4. Next we have to remove the wheel arch trim (fender liner or whatever else you would like to call that piece of plastic german engineering). Fortunately the arch trim is split in two so you only have to remove the front portion of it to get access to underneath the headlight. Part number 51118045961 is the driver's side one. It is held in place by:
1x 10mm nut in the wheel arch
5x 8mm screws also in the wheel arch
4x 8mm screws underneath where the trim meets the bumper
2x 8mm screws also underneath where the trim meets the engine skid plate/cover

Driver's side arch trim, if you follow the screws clockwise starting from the left you have the 5x 8mm screws then the 1x 10mm nut:



Once you have those off, you can remove 4 of the 8mm screws pictured below and pull out the black rubber insert:



The remaining 2x 8mm screws are behind that black rubber piece and pictured below:



5. With the forward wheel arch trim piece removed, you can easily see the headlight control unit (silver) directly mounted under and into the headlight, held in by 2x T20 torx screws. Remove those screws and slide the unit out.

Below is a picture of my passenger side headlight from the wheel arch, the control unit removed. You can see the oil cooler as well as the brake duct. Obviously the driver's side won't have the oil cooler but I pointed out the brake duct just to give you an idea relatively where the control unit is located:



6. Clean the connectors on both ends. I used alcohol and a q-tip for the control unit and a spray contact cleaner for the headlight connection.



7. The 'easy' part, putting everything back together
Just make sure when you place the forward wheel arch trim back in, that it slides above the aft wheel arch trim and above the engine skid plate/cover. Make sure all the holes line up, then and only then start putting the screws back in. Wheels back on. Lower car. Torque down lug nuts. Pray a little. Start the car and see what happens

After cleaning mine, the first time I started the car the fault came on as usual, but after about 2 minutes of driving went away and hasn't come back on for about two days. I will report back after a week to see if that really did solve the problem. Happy DIY'ing!

[Oughourj]

So a week later, the fault still appears once every three or four times I drive the car on startup but now clears itself almost immediately. Problem not solved yet, at least not entirely. Still everything appears to be working normally. Anyone have any suggestions before I invest in a replacement unit?

Update 2:
After some more troubleshooting, I noticed that the driver side headlight turns right, but does not turn left with the steering wheel. The passenger side works fine turns both ways. both cornering lights work i.e. the inner bulbs which light up once you pass a certain steering angle. When the fault is not present the issue still persists i.e. the drivers side headlight still doesn't turn left with the steering wheel. Any suggestions?

[BiscottiGelato]

I thought there's limitation on how much the lights turn left due to on-coming traffic. This is by design. The light moves much less when turning left vs turning right.

That said, I just got the 'Cornering Light Malfunction' issue also... argh.

[thechill]

Awesome write up. Most people with the control unit problems go through the front bumper; this way seems to save a lot of hassle.

Couple questions:
How is it holding up?
If you did have to replace it, do you know if indie shops can do the recode?
How'd you get the $380 figure? I'm seeing $600+ for the unit online.

[Oughourj]

BiscottiGelato you are absolutely correct, the driver's side adaptive headlight will not turn left when the car is stopped for the reason you mentioned; it's actually in the owner's manual. So the headlights were perfectly fine the entire time!

thechill Thanks for the compliment. What's also in the owner's manual is how to get access to that cornering light bulb which is actually from the top of the headlight under the hood. What I ended up doing is opening that up, disconnecting and re-connecting the cornering light and the fault never returned. Total cost: $0 and a bunch of time wasted under the car!! Hopefully you'll be able to resolve your issue the same way or just have to replace that bulb. Best of luck!

[merlinbk]

I've had this problem for at least a year. I've gotten rid of it by replacing the bulb. I've tried different types of bulbs from the expensive ultra white sylvania to more recently the cheap walmart h3. It gets rid of the problem for 2-5 months, but then it returns. In all cases the bulb works fine. Before and after replacement. I'm curious if this cleaning will fix the problem. I sure hope so. I'm tired of having to constantly change out a working bulb. Or worse... the controller.
I wish there was a way to block out that warning. Or find a real fix.

Thanks for the diy I will attempt it and hopefully report back positively.