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Discussion Starter #1
My 2001 e39 525i keeps popping up the asc and abs warning in conjunction with the loss of cruise control. This indicates a right rear wheel speed sensor.
I have replaced the sensor a few times and also swapped left to right but it hasn’t fixed the problem. I have a reader that can show wheel speed data which shows the wheel speed the same as the others when the warning lights are but inbut then knocks it outs when the lights come on,
The warning lights are on must if the time but u can go fir a while with everything working.
So us there a way to find out where the problem is. Why would it work sometimes and then drop out.
Any ideas other than replacing the abs unit?
 

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Wingnut
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have you checked to wiring connection to the WSS? the chassis wires have been know to go kaput.
 

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Discussion Starter #3
Yes. In fact I replaced the coupling to make sure it want a fault at the connector to the wheel speed sensor. Is there a way to check the wiring at the abs box connection to see if there is a short between the wss connection and the abs unit?


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The cruise control on cars with M52TU and M54 engines (which you have) does not come from the rear wheel speed sensors. Cruise control speed info comes from the 2 front wheel speed sensors.
Earlier cars, pre 8/1998, did use the rear wheel speed sensor but not later cars built after this date.
Sounds more like might have a failing ASC/DSC control module.
These suffer from thermal heat soak failures. They work OK until they get hot then you get the trifecta lights.
You need to have the error codes read.
There are up to four modules on the CAN bus, Instrument panel, engine DME, transmission module if you have auto box and the ASC/DSC module and they communicate information with each other over the CAN bus.
If you have communication errors on the three non ASC/DSC modules, the most likely cause is they are unable to communicate with the ASC/DSC module because it has failed, in this case, intermittently.
Google for "BMW MS43 pdf" or similar for more info.
Hope this helps.
 

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Discussion Starter #6
Thanks but unfortunately the fault reader also identifies the problem as the right rear wheel speed sensor. I have an icarsoft bmw reader


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Plan B:
Search for wheel speed sensor testing on this forum or the "Other Forum" and this will give you info on how to test the wheel speed sensors.
You can test them by unplugging the ASC/DSC connector multi plug and test through to each wheel speed sensor.
There is a comprehensive test procedure on one of the above forums but I don't have a link.

Edit:
This link will help.
https://www.bimmerfest.com/forums/showpost.php?p=4205801&postcount=48
 

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Older than old school
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As I just posted in another thread, you can use a code reader like the Creator c-110 or 310 to diagnose your wheels speed sensors. Click through the menu choices ("Chassis" and "Live Data") with the reader plugged into the OBD II port. Then drive the car slowly and look at all four wheel speeds at the same time. The wheel with the anomalous speed has the bad sensor. If all the wheels read the same speed, the problem lies elsewhere.
 
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