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Steering "Dead Zone" with 14' P85D

StoicKiwi

Member
Mar 10, 2019
127
179
San Antonio, TX
I've had an issue for a few months with my early (11/14)Model S P85D and need some help in diagnosing it:

TL;DR: There's a "dead zone" in my steering that offers no turning resistance. Detailed list below paragraphs.

Back in March during a road trip, I did some spirited driving down a mountain on the east coast. Nothing crazy, just having a bit of fun :) After getting on the interstate right after, I noticed that my steering wheel had a little dead zone around the for about 5°. This always follows the top of the wheel (for example, if I turn the wheel so the Tesla "T" is pointing at the 12°o'clock position you can wiggle it in between 11 and 1). In this resistance-free zone, the car will still turn, but offers no feedback to let you know that it is actually turning regardless of steering setting (Normal, Sport, Comfort). This is most noticeable with AP engaged as I can move the wheel in this zone freely. Moving in this zone does not get rid of the "Apply light force to steering wheel" warning message.

After noticing this and getting back home, I scheduled a visit at the Service Center for them to take a look at it and another few things I had as well. They said this was normal and I probably just wasn't used to how to disengage the car from AP(?) I needed my car so I went ahead and took it back and scheduled a Mobile Service visit so I could chat with the tech and explain to him what was going on.

Mobile Service shows up, I explain the issue, and he takes it on a test drive. When he comes back, he says that something definitely isn't right and there is too much play in the wheel. He says that he scoured the Tesla Service database and can't find anything similar to this issue. He says that all of his ideas of what it may be would need to be done at the Service Center. He mentioned: Potential intermediate shaft issue, steering wheel issue, steering rack, or toe adjustment. So I schedule a Service Center visit.

Second Service Center visit was scheduled for last Friday morning (06-18-21), I drop off the car and it sits there until yesterday afternoon (06-23-21) when they finally get it in. This morning they tell me that the work is done. I check out the invoice and they said steering wheel is operating as designed.... They said they tested lock to lock, power assist, and was verified by multiple techs as being "consistent with vehicles of similar age and mileage". They were super busy and were short-staffer so I have a feeling they just wanted this car gone and out of their hair but hey, they did my state inspection 😂

At this point, I've given up on Tesla discovering what the issue is. I still have a year left on my used warranty so I want to at least diagnose it myself to potentially show them exactly what is happening to avoid being blown off for a week to have them spend 5 minutes on my car turning the steering wheel and saying it's good. It could just be in my head but the issue seems to be getting worse and I'd rather not like something to happen and for me to lose steering while driving or something similar. At the very least, it can be difficult to keep the car in a lane while cruising since I don't realize I'm actually turning the wheel.

Detailed list of symptoms to recap:
  • ~5° spot with no resistance while steering
  • Vehicle still turns while in this zone so not a true "dead zone" more like a "resistance-free zone"
  • Moving in this zone with AutoPilot on does not dismiss the "Apply light force to steering wheel" warning
  • First noticed after some spirited down-hill driving
  • Occurs on Normal, Sport, and Comfort steering settings but is most noticeable on Sport due to the lack of feedback
  • It follows the top of the wheel, whichever direction it is pointing
  • When using TM-Spy and Scan My Tesla, the steering angle does show as changing when it is in the zone
Has anyone experienced anything like this before? I searched all over the Internet and the TMC forums and came up empty handed. Any help would be greatly appreciated!
 

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StoicKiwi

Member
Mar 10, 2019
127
179
San Antonio, TX
The only reference I have is from my old ICE car. But you can I'd just have someone lift the front wheels and see if there is any play in the suspension/tie rods/wheel bearings.
Thanks for this! I've got a jack/stands/jack pads, maybe I'll try this this weekend or take it to a local shop and see what they think.

It's almost like a tooth is missing from the pinion or steering rack.
I'd had this thought, but would the car still turn if that were the case?
 

Gtech

Member
Dec 4, 2016
534
647
Netherlands, Berkel en Rodenrijs
I'm also having this issue but not as much as you. Most noticeable when AP is on.

When you enter your car and before pressing on the brake pedal do you feel this 5 degree of no resistance? Try a very softly gentle wriggling.
 

StoicKiwi

Member
Mar 10, 2019
127
179
San Antonio, TX
Was the rack physically inspected for loose or missing bolts? There was a recall for them.

In the times I've had them look at it, they didn't mention inspecting the rack but I'll take out the frunk liner and check. I know the recalled bolts were replaced shortly after I took delivery in 2019.

I'm also having this issue but not as much as you. Most noticeable when AP is on.

When you enter your car and before pressing on the brake pedal do you feel this 5 degree of no resistance? Try a very softly gentle wriggling.

Sorry it's happening to you too, but I'm glad I'm not going crazy.

Yes, when the car is completely off, the resistance-free zone is there as well.
 

Gtech

Member
Dec 4, 2016
534
647
Netherlands, Berkel en Rodenrijs
Sorry it's happening to you too, but I'm glad I'm not going crazy.

Yes, when the car is completely off, the resistance-free zone is there as well.


The belt and motor on the steering rack are not engaged then so the slack is pure mechanical.

As mentioned you could try remove the frunk and check the steering link (green):

shaft.png


If this is not the issue you could check the steering ball tie rods joints but I'm afraid it is slack on the steering rack. I do have a used steering rack here for examination (2015, 100k miles old) but I can already feel there is some radial slack on the ingoing shaft (black). Looks like a failed bearing (yellow) but I'm not sure if yours has the same issue and if that bearing is replaceable.

New steering rack is kinda expensive...3533 euro
 

StoicKiwi

Member
Mar 10, 2019
127
179
San Antonio, TX
The belt and motor on the steering rack are not engaged then so the slack is pure mechanical.

As mentioned you could try remove the frunk and check the steering link (green):

View attachment 677667


If this is not the issue you could check the steering ball tie rods joints but I'm afraid it is slack on the steering rack. I do have a used steering rack here for examination (2015, 100k miles old) but I can already feel there is some radial slack on the ingoing shaft (black). Looks like a failed bearing (yellow) but I'm not sure if yours has the same issue and if that bearing is replaceable.

New steering rack is kinda expensive...3533 euro
I'll pull the frunk off this weekend and give it an inspection. I'll report back and let you know what I find, since this looks quite promising.
Thanks so much for this info!
 

StoicKiwi

Member
Mar 10, 2019
127
179
San Antonio, TX
The belt and motor on the steering rack are not engaged then so the slack is pure mechanical.

As mentioned you could try remove the frunk and check the steering link (green):

View attachment 677667


If this is not the issue you could check the steering ball tie rods joints but I'm afraid it is slack on the steering rack. I do have a used steering rack here for examination (2015, 100k miles old) but I can already feel there is some radial slack on the ingoing shaft (black). Looks like a failed bearing (yellow) but I'm not sure if yours has the same issue and if that bearing is replaceable.

New steering rack is kinda expensive...3533 euro

So after taking the frunk out this weekend, I think I was able to determine what the issue is. It was very difficult to see in the dual motor model, but it looks like either bolt #7 is loose or something is wrong with the intermediate shaft/coupler.
When looking at the shaft while an assistant was turning it, the lower end barely moved and the upper end moved much more dramatically. I took a short video and the only time the lower shaft moves noticeably is when I turn the wheel very hard in either direction.

It didn't like the gif I made of it, so here's the YouTube link for it:

Also, it looks like the bolt was replaced from the recall as well, it looks much newer than everything else around it (see attached picture)
 

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Gtech

Member
Dec 4, 2016
534
647
Netherlands, Berkel en Rodenrijs
So after taking the frunk out this weekend, I think I was able to determine what the issue is. It was very difficult to see in the dual motor model, but it looks like either bolt #7 is loose or something is wrong with the intermediate shaft/coupler.
When looking at the shaft while an assistant was turning it, the lower end barely moved and the upper end moved much more dramatically. I took a short video and the only time the lower shaft moves noticeably is when I turn the wheel very hard in either direction.

It didn't like the gif I made of it, so here's the YouTube link for it:

Also, it looks like the bolt was replaced from the recall as well, it looks much newer than everything else around it (see attached picture)

Definitely something isn't right lol.

Here is the other end of the steering shaft. Think you need some more digging to see where the slack is coming from.

If I find something I will let you know.

shaft2.png
 

StoicKiwi

Member
Mar 10, 2019
127
179
San Antonio, TX
Definitely something isn't right lol.

Here is the other end of the steering shaft. Think you need some more digging to see where the slack is coming from.

If I find something I will let you know.

View attachment 678912
In order to investigate a little more closely, I got out my borescope and turned the wheel.
The whole steering shaft seems to go 1:1 with the wheel until you get right here:
1625063880006.png

Upon inspecting it more closely with the borescope, it does appear to be the source of the slack.
Here are videos I shot (sorry for the low quality) that show it up close:

First video is from the same view as the video I posted earlier, just closer.
Second video is coming up from the bottom and shows better view of difference of rotation of the two shafts.

Does that look like it could be the problem? Is it just secured with that one bolt on the collar that may need tightened?
 
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Gtech

Member
Dec 4, 2016
534
647
Netherlands, Berkel en Rodenrijs
In order to investigate a little more closely, I got out my borescope and turned the wheel.
The whole steering shaft seems to go 1:1 with the wheel until you get right here:
View attachment 679651
Upon inspecting it more closely with the borescope, it does appear to be the source of the slack.
Here are videos I shot (sorry for the low quality) that show it up close:

First video is from the same view as the video I posted earlier, just closer.
Second video is coming up from the bottom and shows better view of difference of rotation of the two shafts.

Does that look like it could be the problem? Is it just secured with that one bolt on the collar that may need tightened?
That could be the issue, I would not drive that car until it is repaired.

Can't believe they told you that's normal.

Yes one bolt holds it in place. You could try to tighten it but i'm not sure it will fix the issue because it should be a tight fit and the bolt is just extra. The shaft isn't exactly round but it's a sort of half triangle.

Try not to overtorq that bolt.

20210630_175019.jpg


16250683576976814514490085351752.jpg


Definitely going to check it on my car also.
 
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StoicKiwi

Member
Mar 10, 2019
127
179
San Antonio, TX
That could be the issue, I would not drive that car until it is repaired.
After inspecting the bolt and seeing that play, I'm definitely not going to be driving it until I get it fixed.

Can't believe they told you that's normal.
I'm as amazed as you are, especially having brought it up three times in different appointments and telling them it was getting worse over time.
This could cause a serious accident if someone just took their word for it instead of investigating it further on their own....

Yes one bolt holds it in place. You could try to tighten it but i'm not sure it will fix the issue because it should be a tight fit and the bolt is just extra. The shaft isn't exactly round but it's a sort of half triangle.
Thanks for those pictures too! I was searching online to try to find a good picture of the end of that shaft to no avail.

Definitely going to check it on my car also.
Hopefully yours is nice and snug and has no play like mine does when you inspect yours.

I'm about to head out of town for a few weeks (thankfully the Mrs. just got a Model Y so the S can stay in the garage) but I'll schedule a follow-up appointment with Tesla and show them what I found. Hopefully they'll understand how serious this could be and not just blow me off again... I'll be sure to follow up with the resolution as well.

Thanks again for all of your help in diagnosing this with me @Gtech, I sincerely appreciate it!
 

StoicKiwi

Member
Mar 10, 2019
127
179
San Antonio, TX
I guess replacing that lower intermediate shaft is not really a 5 min job for a dual motor car 🤔

View attachment 679833
Oh wow, that certainly adds some complexity to this lol

Honestly, I was wondering how to do this since the drive motor, 12v battery, and several other large components are right in front of/on top of it. That's one of the reasons I used borescope to diagnose it as it's remarkably hard to even see in its position.
 

Gtech

Member
Dec 4, 2016
534
647
Netherlands, Berkel en Rodenrijs
Hopefully yours is nice and snug and has no play like mine does when you inspect yours.

Alright, I removed the frunk cover and checked all steering rod connections and it seems that the universal joint from the lower intermediate shaft has some slack.


Very happy that it is not the steering rack itself, will order new parts later this week to fix the issue.
 
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Gtech

Member
Dec 4, 2016
534
647
Netherlands, Berkel en Rodenrijs
Oh wow, that certainly adds some complexity to this lol

Honestly, I was wondering how to do this since the drive motor, 12v battery, and several other large components are right in front of/on top of it. That's one of the reasons I used borescope to diagnose it as it's remarkably hard to even see in its position.

Today I fixed my issue

20210709_175158.jpg


IMG-20210709-WA0006.jpeg


U joint is really bad, besides some slack also hard to rotate.

Car is fixed, I'm happy. Hopefully you will have the same result.

If someone wants to know the part for RWD cars is 1030622-00-A and bolts are torqued with 50nm (37 ft lbs)
 

StoicKiwi

Member
Mar 10, 2019
127
179
San Antonio, TX
That’s great, glad that you got yours fixed (and that it wasn’t the steering rack)!
thanks too for the video as now I’m going to go back and check mine with the borescope once I return back from my trip. I’m curious if there is any play in the U joint on mine or if it is all in the connection to the steering rack.

I may try to find a way to access that more easily without dropping the HV pack too. I’ve read something about getting to it through the wheel well but we’ll have to see.

Also, I’m jealous of the frunk size on those RWD models lol
 

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