Wheel Speed Sensor Fail via CV Boot

splitphaze · 03-06-2023, 05:38 PM

I will start where so many threads never get: the mystery solved (maybe). Now, I just need some input before I test my hypothesis.

2011 535ix

Started with a no-warning slew of diagnostic codes, all seemingly related to DSC communication failure and speed. I eventually deduced that it is probably a wheel speed sensor (or its wiring), which I suspected I might have mucked up when replacing the brake wear sensor recently. (Battery is good, fuses are good, and the issue started so suddenly it doesn't seem consistent with others reporting DSC/ABS unit problems or communication bus issues, although I am receptive to suggestions; see third query below.)

Then, I recalled that I have a slight ticking sound, front right, that seemed to start after an unfortunate speedy encounter with a curb. Voila, the first look revealed a torn CV boot, and dirty dry grease outside of it. Probably original, and shame on me for not preventing this. (I didn't fully explore any other potential issues from the curb encounter, but the wheel otherwise seems to move alright, so flag this issue if you have any suggestions for further inspection.)

What I didn't expect was finding a bunch of wet grease (?) on the left front side. It has been rainy lately, which I hope indicates that slow grease plus fast water equals this slurry. (I haven't researched, but really hope there isn't a mechanism for some fluid from further up the axle to have leaked past a failed seal, and out the CV boot.)

FIRST, I am wondering if there is contamination that got inside the hub and is interfering with the speed sensor. If not, I will still try a known-functional sensor on both sides to see if the errors cease. If not for contamination, what might cause the sensor failure? Damage to the toothed-wheel?

SECOND, I have capability (not so much time) for a project, but wondering whether to replace just boots or the axles. How do I know if the axle has been damaged by the boot failures (since I don't know how long they have been in that condition)? Recommendations for sourcing the boots and/or axles? Any other preventative/routine tasks recommended as part of the process? Shop cost (in 2023 post-inflation dollars) for boot and/or axle replacement? Recommendations in Seattle area?

THIRD, if all of my hypothesis fails, the front end is fixed up, and the codes remain, what do you suggest next?

03-06-2023, 05:38 PM	#1
splitphaze Registered 0 Rep 1 Posts Drives: 2011 BMW 535i X-Drive Join Date: Jan 2022 Location: Washington iTrader: (0)	Wheel Speed Sensor Fail via CV Boot I will start where so many threads never get: the mystery solved (maybe). Now, I just need some input before I test my hypothesis. 2011 535ix Started with a no-warning slew of diagnostic codes, all seemingly related to DSC communication failure and speed. I eventually deduced that it is probably a wheel speed sensor (or its wiring), which I suspected I might have mucked up when replacing the brake wear sensor recently. (Battery is good, fuses are good, and the issue started so suddenly it doesn't seem consistent with others reporting DSC/ABS unit problems or communication bus issues, although I am receptive to suggestions; see third query below.) Then, I recalled that I have a slight ticking sound, front right, that seemed to start after an unfortunate speedy encounter with a curb. Voila, the first look revealed a torn CV boot, and dirty dry grease outside of it. Probably original, and shame on me for not preventing this. (I didn't fully explore any other potential issues from the curb encounter, but the wheel otherwise seems to move alright, so flag this issue if you have any suggestions for further inspection.) What I didn't expect was finding a bunch of wet grease (?) on the left front side. It has been rainy lately, which I hope indicates that slow grease plus fast water equals this slurry. (I haven't researched, but really hope there isn't a mechanism for some fluid from further up the axle to have leaked past a failed seal, and out the CV boot.) FIRST, I am wondering if there is contamination that got inside the hub and is interfering with the speed sensor. If not, I will still try a known-functional sensor on both sides to see if the errors cease. If not for contamination, what might cause the sensor failure? Damage to the toothed-wheel? SECOND, I have capability (not so much time) for a project, but wondering whether to replace just boots or the axles. How do I know if the axle has been damaged by the boot failures (since I don't know how long they have been in that condition)? Recommendations for sourcing the boots and/or axles? Any other preventative/routine tasks recommended as part of the process? Shop cost (in 2023 post-inflation dollars) for boot and/or axle replacement? Recommendations in Seattle area? THIRD, if all of my hypothesis fails, the front end is fixed up, and the codes remain, what do you suggest next?
	Appreciate 0 Tweet Quote