Hi Dan, has this been passed on to anyone else, as i've heard nothing since
Hello XXXXX,
Please do not accept if you feel this is not helpful but I see no one has taken a shot here. My only thought was that maybe the problem is actually in the instrument cluster and not in the ABS system. It is the internal circuit that turns the light on by request of the ABS module. If there is a problem in the circuit that controls the ABS light it will come on even when no faults are present. Maybe this is actually a false warning and that is why no codes set. Just an idea. I can always opt out but I wanted you to know what I thought it might be.
(Hello. You posted just as I was updating this. I hope I have explained well enough below to help you. I am in no way certain if this is the cause...but I have had a short be the cause for an ABS light to be on at one point many years ago. That is why this such an interesting but difficult problem.)
If it is the instrument cluster that has a problem internally in the circuit board it would mean an instument cluster replacement. It could also be a problem in the wiring circuit of the ABS control module and the instrument cluster. Although the short could be in the wiring harness. I have tried to find the exact wiring diagram but there are too many to choose from depending on the DME version and ASC version. If I had the vehicle in the shop and this was something that can be easily reproduced as you described at idle or at a start, and there were no fault to go by. I would want to run a new wiring harness in the circuit for the lamp from the ASC to the cluster and see if it still had the problem. If it the problem stops then it shows it is in the harness. If it continues and there are no faults and the ASC has been replaced already (as this module plays in the activation of the lamp) then it makes the cluster as a potential reason for the false light.
I might be able to find the correct wiring diagram if I knew the DME version and the ASC version.This is the choices I see.
I am not positive if I am on the right track but since everything else was replaced it makes this a real possibility.
BMW Mechanic
Level 1 BMW Master Certification, 9 Years Dealer experience, Team Leader, Shop Foreman
Thank you for your accept XXXXX. I hope I have led you in the right direction with this problem. I wish I could take a look at it myself as this certainly sounds like a hands on type of problem to solve. I wish you a lot of luck!