Uber annoying ABS/ASC lights

[m3f_Brouhaha]

My car has the nagging problem of the ABS-ASC lights coming on seemingly at random. It doesn't do it consistently. I might drive the car two or three times and then bang there they are, hello! Then if I shut the car off and restart it the lights will go away and won't reappear for a while.



It was doing this with far greater frequency last year so I replace the control module with a used one off of another M3. Now it does it much less often but still does it on those rare and very annoying occasions.



I checked my abs sensors with a multimeter and got nothing. They all seemed consistent at about one ohm. And I would think that if it was a bad wheel sensor, it would set off the lights more frequently.



I can take it to the dealer to have them read the code of course but I didn't like the way they said it's $170 just to get started, lol! I have a feeling they will just start throwing parts at it and we will finish well into the four figures if I do bring it there.



Let me know what you guys think. Thanks in advance.

[m3f_betrezra]

I bought an ebay BMW laptop-interface scanner.... it was around $200. Should help me diagnose my Airbag light, and rondom ASC Light.


You will have to do the same thing as dealer.... check for codes.... and hunt-peck/change parts until it goes away. Hopefully the code reader will save you time/$ in the long run.

[m3f_frbz]

Mine was the pedal travel sensor

[m3f_Brouhaha]

I bought an ebay BMW laptop-interface scanner.... it was around $200. Should help me diagnose my Airbag light, and rondom ASC Light.



You will have to do the same thing as dealer.... check for codes.... and hunt-peck/change parts until it goes away. Hopefully the code reader will save you time/$ in the long run.

They will sell me hope like a hospital pushing experimental treatment to a patient who desperately wants a cure. So it's probably a good idea that I get the tool. At least it will be cheaper as I throw parts at it.



But will it work to read the ABS codes? I brought it to an independent mechanic who said he couldn't read the codes off the computer and suggested that I get the new module. That $65 piece of sage advice didn't work out well for me.



As to the pedal sensor, I don't know if that's it. A lot of times the light will come on when I'm just driving and haven't even touched the pedal. Did yours do that?

[m3f_Brouhaha]

Mine was the pedal travel sensor

Whew. That is one pricey little part. $137 for a sensor. I have no doubt that's due in some part to the fact that it's just a little bit more to diagnose it, so they figure that you will pay a little less on the chance that will solve it. I guess the comfort would be that the dealer would probably charge you about $800 for the part plus installation.

[m3f_englishtom1596q]

When you check wheel sensors you're not checking resistance. You need to spin the wheel and make sure it produces voltage. Either way I doubt they're your problem as they're rarely intermittent when failing. Just for future reference.

[m3f_Oogie_M]

I had the same issue as you. Per the suggestion here, I tried cleaning the wheel speed sensors first:



http://www.m3forum.net/m3forum/showthread.php?t=401685



I had a new wheel speed sensor so I swapped it in at each hub to see if it was specific to a particular axle. But the problem did not go away.



Then I bought the brake pedal travel sensor, replaced it and no more lights. Apparently the soldering inside break apart, so it doesn't matter if you're touching the brake pedal or not.



https://www.bimmerforums.com/forum/s...ch-ABS-DIY-Fix

[m3f_Brouhaha]

When you check wheel sensors you're not checking resistance. You need to spin the wheel and make sure it produces voltage. Either way I doubt they're your problem as they're rarely intermittent when failing. Just for future reference.

I understand you should get a base ohm reading and then check for uniform escalating voltage on rotation. I didn't bother with the latter part because I'm kind of in your school of thought. If there was a problem with a wheel sensor that I could read with an $11 Sears multimeter by simply rotating the wheel, then the sophisticated Bosch ABS computer would throw the lights on immediately and every time right?


This brake pedal travel sensor seems to be a common problem on these cars and, from my research, would lead to the random behavior that I am experiencing for the reasons oogie describes. The question I am weighing is whether I just replace it and hope for the best or whether I have an independent shop attempt to read the codes - one with better equipment than the original one I brought it to. Not sure I can justify spending that much on a tool that I'll probably only use once. I will keep updating this as I learn more information.

[m3f_frbz]

All the modules have to be accessed with the round connector under the hood. All the OBD 2 connector will do is talk to the engine control computer

[m3f_Oogie_M]

The question I am weighing is whether I just replace it and hope for the best or whether I have an independent shop attempt to read the codes - one with better equipment than the original one I brought it to. Not sure I can justify spending that much on a tool that I'll probably only use once. I will keep updating this as I learn more information.

I have the Schwaben BMW tool (ECS told me it can read ABS codes). Although the unit couldn't detect any codes or errors when I scanned it with the ABS/ACS lit up. Might need to find a shop with an actual BMW GT1 diagnostic capability.