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Another Tesla service center experience and warning for those doing their own suspension work

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Back in the spring of 2020 when my car was only a few months old I installed Mountain Pass Performance Coilovers. Little did I know that over 2 years later, a small oversight when installing them would cost me $429. I've been working on cars for over 2 decades, and even the most experienced of us can make small mistakes.

Fast forward to last month. I was driving from Chicago to Indianapolis. I-65 in Indiana is a notoriously bad road. Lots of uneven pavement, large bumps, potholes and dips galore. I went through a large dip in northern Indiana and the car freaked out. I lost ABS, re-gen, power steering and all driver assist features. I had to pull over at an exit, put the car in park, get out, close the door and then get back in to re-set everything. This happened 3 times on my way down to Indy and another 2 times on the way back even though I was driving extremely cautiously by that point. Through the course of those 5 occurrences, I narrowed the issue down to the front left wheel. I figured the wheel speed/ABS sensor was the problem. Ended up that I was right, but it wasn't Tesla's fault directly and it wasn't a faulty sensor.

It turns out that when I installed the coilovers and re-installed the wheel speed sensor wire on the upper A-arms, I used the wrong mounting point on the rear part of the A-arm. There are two rear mounting points about 1.5 inches apart and the correct one is kind of hidden on the inside rear of the A-arm. I hadn't paid really close attention when I removed the line, because you usually don't have extra unused mounting points for wiring on suspension parts. As you can see the in pic below (taken when I installed the suspension!!!), there is extra slack in the wire between the two mounting points. That extra slack should be between the rear most mounting point and the speed sensor plug on the inner wheel well to allow the front wheels to turn. The way I hooked it up, the speed sensor wire would stretch every time I went full lock. Even though I did that it still took over 2 years to become a problem.

I had taken the car into Tesla instead of simply putting the car on my lift at home because I figured it was a Tesla warranty issue. Well, once they had it all apart they identified the problem and it definitely was my fault. I saw it first hand and talked to the mechanic. The SA and mechanic were very understanding, but the cost still comes down on me since it wasn't a factory problem. I was able to get the car in quickly and the SA was in constant contact with me. I have a loaner 3 LR until tomorrow and they are only charging me $130 labor to replace BOTH front wheel speed sensors. Therefore I decided to just let them do the work instead of buying the sensors and installing myself. Every service experience I've had with Tesla has been fantastic.

If you are doing your own suspension work, be very aware of the mounting points for the speed sensor wire on the A-arms!!!!

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It's obvious that you would lose ABS (and any stability control) and maybe re-gen if Tesla has strange redundancy logic but there is no reason to lose power steering for speed sensor glitch. How difficult was it to steer the vehicle after the malfunction. I wonder if Tesla deliberately cuts power assist to the steering so you don't ignore safety faults like an ABS/stability failure.

The speed sensor is a simple passive coil but it's signal is very small and it doesn't take much to disrupt it. That's why there won't be a connector at the sensor, its too easy for moisture/grime/corrosion to stuff up the signal there.

Your wheel arch area looks to be in as new condition, did you give it a clean up before the pic or does it always look like this. Neat that the car colour matches the coils although you wouldn't see it when the wheels were on:(.
 
It's obvious that you would lose ABS (and any stability control) and maybe re-gen if Tesla has strange redundancy logic but there is no reason to lose power steering for speed sensor glitch. How difficult was it to steer the vehicle after the malfunction. I wonder if Tesla deliberately cuts power assist to the steering so you don't ignore safety faults like an ABS/stability failure.

The speed sensor is a simple passive coil but it's signal is very small and it doesn't take much to disrupt it. That's why there won't be a connector at the sensor, its too easy for moisture/grime/corrosion to stuff up the signal there.

Your wheel arch area looks to be in as new condition, did you give it a clean up before the pic or does it always look like this. Neat that the car colour matches the coils although you wouldn't see it when the wheels were on:(.
The electric power steering assist, cruise control, and traction control are all tied to the ABS wheel speed sensor. I'm having the same issue as the wire on the passenger front rubbed through after installing my winter tires that were slightly wider with more tread than my summer tires.