tlwright21

My 2008 535i threw this message 2 days ago. Thought at first the bulb went out but it seems to be a intermittent issue. The bulb will light up upon engine start up but then goes off and gives the message. Pulled the headlight unit last night and inspected all wiring. Everything visually appears intact. Nothing loose and no problems with the wiring insulation, so what is causing the problem if it is not the bulb. there are couple of very expensive parts that I'm wondering could cause this, a control unit and something else I read about. If so how do you test them? Any suggestions on what to do next??? I can replace the parts myself if I only knew which part to replace.

KyleB

Is just the one side doing this? If so I'd swap bulbs from side to side and see if the problem follows the bulb. If it does, you know what you're problem is.

I just dealt with a customer that had a nearly identical problem with her Lexus. We replaced the bulb and that fixed the problem.

cinergi

HID bulbs are not like incandescent bulbs, which either work all the time, or not at all if they are burned out. An HID bulb can fire successfully but then be unable to sustain the arc. A bad ballast can also cause this symptom.

As Kyle suggested, swap the bulbs and see if the problem follows. If it does, it's the bulb; otherwise it's the ballast.

cinergi

tlwright2

thanks for the advice. I did as you said. The problem followed the bulb swap, so I called BMW and they wanted $230 for a bulb, then called Oreilly's they wanted $100 for the same Sylvania Osram D1s bulb. no brainer there. was certainly scared for a minute that that was going to be another stupid BMW dealer visit.

KyleB

Awesome, glad it worked for you. Score one for the good guys!