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Improper tire size?

So I had my falcon doors replaced by the mobile ranger last Friday morning in my driveway. When I came back hours later and tried to drive the car, a ton of error messages popped up immediately of no power steering, traction control, stability control, and park assist. Multiple resets with the scroll buttons cleared the errors. The ranger tried disconnecting the 12V, and that also did not work.

The car ended up getting towed to the SC. They just called and stated that they are detecting a wheel speed sensor error. The car’s rear tires were replaced last June with 275/40/20’s. The SC stated that is likely causing all the errors as the X comes fitted with 275/45/20’s.

This seems like such a trivial difference that the car’s computer should be able to take into account and compensate especially when the X already comes with a staggered set up, especially when many of these cars are thrashed around on the tracks which I would think would make the wheel speed sensor go bonkers.

Now the SC want to replace my rear tires which are less than a year old but said they cannot guarantee that will solve this error problem.

As an aside, whether or not this might be related, the front passenger tire was mounted backwards. Apparently some non-direction tires still have to be mounted in only one direction, with one sidewall labeled “inside” and the other sidewall labeled “outside”.

Thanks in advance for any thoughts/suggestions.
 

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The way you are framing it, the natural conclusion is there's no way these errors have anything to do with the tire size and have everything to do with some unrelated computer issues that cropped up right after the falcon wing doors were replaced. Do I have this right?

The difference in diameter going from 45's to 40's is not trivial, it's a full inch, and you go from about 700 revolutions per mile to 725. That's what, 3.6%? That might be exceed the acceptable tolerance.

They might legitimately want you to fix your tire situation just on general principles. I imagine they do have to make some effort, by law, to keep the accuracy of odometer readings within some kind of range.

But tying that to the software issues that suddenly materialized after a service visit does seem a little dubious.

I particularly wonder about the famous 'park assist unavailable' bug that has been cropping up randomly for all kinds of folks for a year now. Pure software bug.

Now the SC want to replace my rear tires which are less than a year old but said they cannot guarantee that will solve this error problem.

Yep. That's it in a nutshell.
 
I just ordered replacement rears. Will see if that clears the errors. I still do not see why out of spec tire size would cause the car to lose power steering.

So yes, all three things(falcon door repair, “wrong” rear tire size, and losing PS, SC, TC and brake regen) seem completely unrelated, at least to a layman like me.
 
This is exactly what I would expect to happen

How will the car's computer take it into account? It's designed around the same size all around (19" snow setup), or larger tires in rear, and you've got significantly smaller tires in the back. It can only see what the sensors tell it and the sensors are telling it the rear tires are spinning too fast

I have owned a few cars with staggered setups and if you put a short tire on the back, they all have thrown some kind of error or the stability control has gone nuts.

Fix the tire shop's ****up
 
Did you change the fronts too, or just the rears?

This behavior will also appear when there's a wheel speed sensor issue. It could be the sensor has failed, or the wiring has been damaged. A week or so after my 19" square winter wheels and tires went on, I had a similar issue. It ended up that the front wheels were rubbing the sensor wire and had caused it to fray.
 
Did you change the fronts too, or just the rears?

This behavior will also appear when there's a wheel speed sensor issue. It could be the sensor has failed, or the wiring has been damaged. A week or so after my 19" square winter wheels and tires went on, I had a similar issue. It ended up that the front wheels were rubbing the sensor wire and had caused it to fray.
 
Did you change the fronts too, or just the rears?

This behavior will also appear when there's a wheel speed sensor issue. It could be the sensor has failed, or the wiring has been damaged. A week or so after my 19" square winter wheels and tires went on, I had a similar issue. It ended up that the front wheels were rubbing the sensor wire and had caused it to fray.
No, I did not. All four tires have less than 10k miles easily so I didn’t want to empty my wallet switching out all four.

Tires are arriving tomorrow so hopefully will have a more definitive answer by end of the week.
 
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SO IT WAS NOT THE TIRES THAT CAUSED THE PROBLEM!

About three weeks ago, the same exact problem arose when I had just returned home to pick up something before venturing out again. Just after 10 minutes of sitting in the driveway, the touch screen spewed out all the same error messages again. I tried resetting the car and it would not even reset. After about another 10 minutes, all the errors cleared spontaneously.

Two weeks ago, I was out taking care of errands before work. When I got back into the car to drive to work, the same errors came up for the third time. This time, it did not self-resolve. Resets also did not work. As I had work to get to, I ended up driving around in a 5000lb car with no power steering.

When I finished work, just as I suspected, the errors disappeared. Not wanting to take any more chances, I drove straight to the SC and told them this needed to be looked at asap.

Fast forward to two weeks later, I still have not gotten my car back or gotten any answers as to what is going on. The first ten days, the car apparently sat at the SC waiting in the queue. When I checked in a few days ago, I was told that a master technician would need to be assigned to my car with it being an unusual issue, so it got moved to a different queue.

Here are two details that are currently pertinent to this serious problem:

1. The cause was definitely not the wrong sized tires as they have been replaced with the correct factory-spec tires and I had two episodes afterwards.

2. This may be a coincidence, but I am now noticing a recurring pattern where each time this issue came up, the car had been outside in 80+ degree weather.

I searched the forum and came upon a few threads where MS’s and a couple MX’s had similar issues, but some of them occurred during relatively cold temperatures. There was something about a faulty harness or grounding that was giving those cars the errors.

Thoughts?
 

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Every time I message or call them, I just keep getting the “car is currently in queue” response.

I sent a message through the Tesla website earlier this evening and will try to contact someone on the chat tomorrow. The other annoying part is I did not get a loaner all this time. Ubering around while lugging kids’ booster seats is a huge pain. Quality of service is definitely not what it used to be.
 
FWIW, I still think checking the wheel speed sensors is a good starting place.


That's reasonably well documented as a cause of the multiple systems becoming unavailable like you're experiencing for the S and X.

ETA: My issue started as intermittent as well, and over a couple days got to the point where the wire was completely severed and the systems remained offline. Fortunately, the old Service Manager at one of the local SC's was great about getting me in (driving around an X without all those systems during a Minnesota Winter is not exactly safe).
 

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