first make sure the bulbs are good . next try replacing the headlight relay, if that doesn`t do it it is most likely the light switch itself
I had this problem on an '02 525i. The socket in the wiring plug was corroded. Replaced it and no problems since, over 1 year now.
If both lowbeam headlights fail at once, it probably isn't the lamps themselves. That would be a fluke. The wiring is usually not at fault. It is vulnerable at the ends where the connectors are because they might become corroded. Check that last. That leaves the two other vulnerable points in the circuit: the fuse and the light switch. Check them out.
Most can be replaced by you fairly easily. See your owners manual. For a rough idea on what the price is on the actual lamps, see sources and related links below.
There are two different bulbd, 1 for dipped beam and 1 for full beam.
Look under passenger side dash right below heater core for relays
Lowbeam is an H7, highbeam/DTR is also H7
blown fuse/blub on the lowbeam is pop/wiring is messed up
1) Open front hood. 2) Twist lowbeam connector from back of headlight casing. 3) Twist apart bulb from the connector. 4) Replace with new bulb. 5) Reverse order of above steps to finish.
The circuit requires the hi/lo switch. You'll need to get a replacement switch for everything to complete the headlamp circuitry.
The bulbs screw in from the rear and if you can't get to the rear, you have to take the light assy off.
Just replaced the headlight bulbs in a 98 Grand Cherokee that had the same problem. It had the wrong bulbs in it. It had 9007's in it. Calls for 9004's.
PULL the light switch out (must be in lowbeam setting for fog lights to work)