How to cure the E36 Brake Light OBC

[Peter Rossato <rossato@xxxxxxxxxxxxx>]

Lorenzo, et al,

I too was plagued by the mystery "Brake Light Circuit" message on my
OBC.  I would check my lights and they were working properly.  By
turning the car on and off the message would reset and then a few days
later it would come up again.
I recently went to the dealer for a few minor things and mentioned to
the mechanic that I was getting false check messages out of the OBC.  He
solved the problem and gave me an insight into what the cause.  The OBC
does a continuity (resistance) check through the bulb and will pop up a
message if the resistance is not in spec.  For this reason he warned me
to use only BMW bulbs because they fall within the OBC expected range,
whereas what you find at the typical auto parts store may or may not.
He popped out a bulb, scraped off the housing contact and the bulb
contact with the tip of a small screw driver.
The system must be very sensitive to minor resistance changes because by
removing the minor layer of oxidation on the contacts the problem went
away and I have not had an OBC check message since.  I followed up on
the mechanics advice and bought a couple of BMW bulbs from the parts
counter so that when they eventually blow I can avoid false warnings.
Try cleaning your contacts, if this doesn't help, try new BMW bulbs.

Peter Rossato
'94 325is "VDERZEN"

------------------------------