This is caused by the cars system checking to see if your low beam light circuit is closed meaning the H7 bulb's filament is still connected. If it is cut or burned out, then the check lowbeam lights kicks on.
If you have not replaced your H7 bulbs to HID then your low beam H7 bulb(s) needs replacement.
If you've upgraded to HID lamps from H7 bulbs then you'll get the CHECK LOWBEAM LIGHTS Message.
Since HID's use a ballast and the bulbs in HID's do not have a filament but xenon gas to eluminate the lamps, this causes the system to think the old H7 bulb is burned out.
You have few options, build a resistor pack like the one pictured below that will fix this error message. Install City Lights to or Purchase a Hella resistor pack to resolve the problem.
Building your own resistor pack by Lefty.
Xenon upgrade fix.
Problem: When upgrading to Xenon Lights from halogen an error message displays saying "check lowbeam". This is because the computer is expecting a certain resistance from the presence of halogen bulbs. By upgrading to xenon the resistance is incorrect. This error only occurs when lights are turned off. This solution is creates a switching resistor that turn off when the light are turned on. The resistor packs that you get from Hids4less or other vendors are "always on" resistors that provide resistance even when lights are turned on.
Notes: This fix is intended for the 5 series e39. This solution make work on other cars, but ONLY if the error message displays when the lights are turned off.
Parts: All the parts can be obtained from Radioshack.
2 - 3x2x1.5 inch project boxes
4ft - wire
4 - crimp connectors
2 - 12 volt relays that provide a closed circuit during loss of power. Radioshack part# 275-218
2 - 12volt 20watt halogen light bulbs
Instructions: Make all connections according to the diagram below. I recommend soldiering the connections.
The completed boxes should look like this
I stuck the boxes right against the ballasts. Verify that your resistor boxes work with an OHM meter then measure the resistance of one of your old halogen headlight bulbs they should be the same. When attaching the resistor boxes make sure you attach them to the 12volt leads that go from the car to your ballasts (your old halogen connectors).
Lastly, if you find that you almost set the house on fire the last time you whipped out a soldiering iron. You can email me at email@example.com and for $100 plus shipping I will make you a set of resistor boxes. I prefer that you make your own considering that it's only $35 for parts.
Link to Installation Guide
Link to similar resistor pack by Greg-NJ
Install City Lights to your low beam head lamps
by R Burns on December 19, 2000
To install a city light kit to eliminate the check low beam you need to do the following:
If you have factory headlamp housings you may need to open up the holes at the top of the high beams. It is marked, just not knocked out - carefully drill through the black platic housing. If you have replacement lights the hole will already be there and plugged with a gray plastic plug.
I tried several different light sockets - the ones that worked best for me were from the side fender mounted turn signal off my 1994 E-34. The dealer should be able to help you find the right size - places such as Pep Boyz have nothing that will work. These sockets hold standard size 5 warr marker lights - I think bulb #168 or 194? - you can use either clear or amber to your preference.
Just splice the wires for the city lights into the wires for your low beams close to the headlight unit - and no more check low beam warning.
The most inportant thing is that if you do have to drill the hole in your housing unit be careful doing it, use a drill bit that does not have a course thread because it can catch an edge and break off excess material and the socket may not fit securely. Probably if you have access to a Dremel tool to bore out the hole that would be best.
If you need pictures or anything let me know.
Hope this helps,
Purchase a Hella Resistor Pack
A resistor pack can be purchased from hid4less.com for $139.99*
* Price quoted off of their web page as of June 2002 for both units.
Section : Projection Housings w/ Angel - Eyes (E39 Halogen To Xenon)
To order the resistor pack, click on the 139.99 from the hids4less.com's web page