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My Mechanic cant solve it and neither could I

1419 Views 20 Replies 8 Participants Last post by  Paul in Boston
TLDR: Neither I nor my shop can find what the issue with my DSC is

My 2006 BMW X3 146k is limping along. I am trying to get rid of the annoying "holy trinity" of lights. My work started with a clunking front end when driving and the 4x4 DSC and ABS lights coming on with the clunk. I got rid of the clunk noise when I replaced all 4 calipers, and both front CV axles. The front passenger CV axle had broken at the U joint. While doing this work I managed to break one of my wheel speed sensors. I replaced it with a wheel speed sensor from O'Reillys. I believe it was the front left.

I have now been chasing the codes that still come on the dash whenever I gas medium or brake medium. The car gives a slight hesitation when it gives this fault condition and the lights on the dash come on with a beep. Ive verified that the wheel speed sensors are reading correctly by plotting a graph of the sensors readings.
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The codes that my scan tool currently bring up are 5DEC transfer case malfunction, 5E5C Wheel speed sensor direction-of-rotation detection, and 5EB1 steering angle sensor supply.

I have tried taking the car to my local shop, a reputable mechanic I trust a lot. When I first brought it to them they said that the SAS was far out of alignment, that they reset that and the problem should be fixed. The light came on the next day. They said they were unsure of the issue and they proceeded to do the free transfer actuator repair seen on here. They gave me the car back and the light came back on the next day. I brought the car back, they held the car for a few days, I didn't mind as they hadn't charged me for the work on the actuator, and then after about 5 days they said to come get the car. They said that they're pretty certain its the transfer case itself, and advised that I continue to drive the car until the transfer case fully breaks, rather than pay 2k right now for a new one.

I would really like to get a full answer of the problem, Im more than willing to try any and all diagnostic suggestions but I've really ran out at this point. Any help would really be appreciated.
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FWIW, check the starboard rear axle near the tone ring for scale or flaking paint. I traced a triad of lights and SAS code that ONLY appeared on a very specific instance (slight uphill on a 90* right turn at 5-10 mph, with front tires on ice) to scaling paint on that axle. During suspension unloading and front tires slippage, the DME got confused. I pulled that WSS, stuck a pipe cleaner in the hole and rotate the axle to clean it, then acid treated the axle. The starboard rear reluctor is usually the first to fail.

I’m not saying that’s your issue, but is an example of why codes are not absolute.

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So all 4 of my steering knuckle assemblies are rather rusty. Do we think I should take out each wheel speed sensor and try and clean them? What acid do you use to clean it? Muriatic?
I use Ospho for all my metal-preps, but any acid will do, even vinegar. Soak, rinse, done.

On your graph, the wheel speeds diverage at the end; what happened there? Make a turn? You may want to look down the WSS bores with a light while spinning the axles to look at the entire reluctor, and take a depth measurement with a caliper in at least the 4 quadrants to be sure the reluctor isn't being lifted by rust. A little ring lift coupled with a little bearing play could bring an error during loading/unloading of the rear suspension; just hypothesizing there.
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(y) I usually don't bother with degreaser as it won't affect magnetism unless it is antiseize; it shouldn't be greasy anyway unless your wheel bearings are failing or CV boots are cracked. If so, you'll never not have a WSS issue. Definitely use a catch basin so you don't acid wash the shop floor.

I'm also not saying that will solve your issue either, but I find it prudent to establish a baseline before diagnosing further. I despise rust and try to correct it every chance I get. Make sure to wire-brush the knuckle surface where the WSS sits to ensure it is seated fully.
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