As I was doing some pre-purchase research on the E39 M5, I realized that the 02-03 models offered a feature I really wanted: Automatic Headlight On/Off. While it seems trivial, all my other cars have this feature and I've grown to like it (read: I'm lazy and spoiled). First World Problems.
As luck would have it, I came across a very low mile 2001 (Build 12/00) model and simply couldn't pass it up, so I bought the car despite it missing this feature. My hopes were to retrofit Auto Headlights after I took care of some other maintenance and repair work.
Much of this info came from http://www.e39.org.uk/autolights.htm, so this DIY is an attempt to condense some of the info, shed some light on the required coding, and show some pics from a car with the steering wheel on the correct side.
Thanks to Adam (Clemster) for hooking me up with a great deal on a matched set of components to perform this swap! As always, perform this at your own risk - I am not liable for anything!
Parts you'll need:
- LCM IIIB (Light Check Module)
- RLS (Rain & Light Sensor)
- 4-position Light Selector Switch & Bezel
- RLS adhesive pad
Tools you'll need:
- Torx driver
- Phillips Screwdriver
- Various trim removal tools
- 19mm socket
- Small flat screwdriver
- Heat Gun (hairdryer might work also?)
- 8mm socket and ratchet
- Laptop with PASoft's BMW Scanner software and OBD-II head.
The Automatic Headlight function is controlled by the LCM and it looks for two inputs when deciding whether the lights should be on or off: the light selector switch should be in the "Automatic" position (Max counter-clockwise) and the RLS should be reporting that the ambient light level outside is lower than the specified threshold. Easy, right?
The 2000-2001 cars came with a LCM IIIA, which isn't capable of handling this function, so we'll need to upgrade to a LCM IIIB, preferably from a salvaged M5. I believe this LCM is available from other BMW models as well, although I'm unsure exactly how the coding would need to be handled. Ditto for the LCM IV which is also rumored to work for this application. M5 build date you are looking for is 9/2001 or later.
Assuming your M5 came with automatic wipers, there is a rain sensor (RS) located on the inside of the windshield, just below the rear-view mirror. This sensor will need to be replaced with a RLS in order to add the ambient light functionality.
The Light Selector Switch on the 00/01 cars is a 3-position switch: Off/Parking Lights/On. We'll need to replace it with a newer switch and labeled bezel that adds a 4th position to the left of "Off", which is the Automatic selection.
Again, easy stuff as this is all plug-and-play with no wiring changes needed.
Light Selector Switch Installation:
Pull on the selector knob and it will pop off, revealing the plastic 19mm nut which secures the light switch to the cluster bezel. Loosen the nut with the socket, but don't remove it yet. Remove the cluster bezel by popping off both pieces of wood/titanium trim and removing the three Phillips-head screws. Also remove the three Torx screws at the top of the cluster bezel and the bezel will pull toward you. At this point, you should be able to access the rear of the light switch. Unplug the single connector and remove the 19mm nut. Reassembly is the reverse of above - be careful not to over tighten the 19mm nut...it doesn't take much force to hold the switch in place.
The LCM is located in the passenger-side kick panel, below the glove box. There are lots of DIYs and videos out there that can explain this better than I can, so I'll refer you to YouTube for this part. I would recommend taking a close-up picture of the label on your new LCM in case you need to know part numbers or sw versions later on. Before removing your old LCM, use BMW Scanner or NCS Expert to note your specific LCM coding options so you can manually apply those to your replacement LCM.
Not my video, but here's a how-to I found on YouTube:
How to remove LCM on 1998 BMW 528i E39 - YouTube
For reference, my new (used) LCM-IIB
Remove the trim around the rear-view mirror mount by prying it apart with a small screwdriver. Once it's popped apart, remove both halves. Remove the rear-view mirror by grabbing the mount and rotating it counter clockwise about 45 degrees. Unplug the electrical connector and your mirror is now out of the way. Remove the RS by prying out the plastic retaining clips from both sides. The sensor should pull off the Prism, which is glued to the windshield. Unplug the RS and set it to the side. Now you need to remove the prism from the windshield. Note that the Prism on the RS is made of glass, so prying on it is not advisable. The adhesive is a gelatin-based "goo" that is similar to what holds a new credit card to it's paper. I found that heating the prism up with a heat gun allowed me to get a plastic trim removal tool wedged between the windshield and the prism and pop it loose. Clean the windshield by "rolling" the adhesive from one side with your fingers, just like you would a credit card. You should be able to get the bulk of the goo off with your fingers and carefully follow up with a razor blade and some glass cleaner for the last few bits.
At this point, the RLS opening on the windshield should be crystal clear and ready for a new prism.
Take the RLS off it's plastic prism by sliding the locking tabs up and removing the prism. Keep in mind that the electrical connector for the RLS will end up in the upper right hand corner once installed so make sure you orient the prism correctly. I ordered two type 903 pads from:
RAIN SENSOR PAD REPLACEMENT 903 (Pad only)
903 RAIN & LIGHT SENSOR KIT (Pad & Prism)
Although you only need one, I'd recommend buying two so you have an extra just in case. Each pad comes with instructions and a tube of 3M primer. Apply a light coat of primer to the windshield and let dry for >5mins. Same for the back of the prism. Once the primer is dry, peel off one side of the protective plastic and attach the pad to the prism. You can eyeball it and put it on centered. Once that's attached, peel off the other side of the pad and have a friend help you center it on the windshield. Attach the RLS to the prism and engage the locking slides. Plug the RLS in, re-install the rear-view mirror/trim and you're done!!
RLS Part Numbers for reference: