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An issue which has stumped Tesla Repairs for the last 2 years

I have an unusual situation with my 2018 Model S -- spontaneously while driving my power steering stops working and my dash starts cycling through several error messages, some of which included (video link):

  • Steering Assist Reduced (followed by power steering being disabled mid-drive)
  • Park Assist Unavailable
  • Lane Departure Avoidance features unavailable
  • Regenerative braking temporarily reduced
  • Automatic Emergency Braking reduced
  • Stability control disabled
  • Traction control disabled
Autopilot disables as well and sometimes at red "P" displays on the upper right saying something like "Parking Brake Disabled".

This began ~2-3 years ago, and I have had multiple previous visits at Tesla during which they said they couldn't reproduce the errors or that the issues were resolved, but they have inevitably recurred. The issue used to be rare but now happens much more commonly, coming back in full force after the most recent update (which I tried to avoid but self-installed anyways). Now the power steering drops out while mid-drive about 7 out of 8 times when I take it out, which has put me in some dangerous spots. Even more confusing, I recently had a mobile visit where the mobile technician also noticed these problems and thought it might be the 12V battery, but he then sent me the following text afterwards:
Something very strange is going on. The alerts that I saw when I was at your house can't be found. It's strange because it's historical data that doesn't get deleted. I'm super confused. If you could reach out to me next time the car acts up, I can try and catch the alerts. I think this is why the diagnostic team couldn't find anything. It's literally not showing up anymore at the time stamp I was at your house.
He's since set me up with another in person visit which I will have later today. I have a sneaking suspicion that they will say the same thing -- that the errors aren't able to be reproduced or that the issue is fixed only to have it recur after I pay the bill and go home. Possibly related is that the coolant pump stays on after I park even when not using AC. I had a bad hit and run in 2018 where I was struck severely on the front left while I was driving, wonder if this is a residual issue though I don't think I could prove this to insurance ($35k worth of damage at the time). The mobile technician thought it might be a 12V battery issue, but he is really confused as to why the errors aren't registering with Tesla's main server. Also, replacing the 12V doesn't come up as one of the error messages (though perhaps it wouldn't if related to one of its connections and not the battery itself)?

I've put a pretty penny into the diagnostic work up trying to figure this one out and am dreading my visit with Tesla Service later today as being another Groundhog's day. Have any of you had similar issues or any thoughts as far as troubleshooting?

Any advice would be sincerely appreciated!
 

SoCal Buzz

Early Adopter
Supporting Member
Oct 9, 2018
938
884
OC, Calif.
If not a grounding issue, I would venture wiring harness. Intermittent and unusual errors (if not firmware related) seem to tie back to electrical faults whether grounding or a harness that’s pinched, cut or otherwise damaged.

It took Service Center weeks to diagnose strange suspension errors on my 2018, that eventually traced back to 1 harness.

Unfortunately that is difficult to isolate.
 
Here's a similar issue. The grounding issue generated other unrelated errors:

 
I have the same issue '21 Plaid MS last week. Have another co worker with a Perf MY who had the issue the day after mine first happened. Exact same faults. Happened to both of us during hard acceleration form stop lights.
20220420_173936.jpg
 
I have an unusual situation with my 2018 Model S -- spontaneously while driving my power steering stops working and my dash starts cycling through several error messages, some of which included (video link):

  • Steering Assist Reduced (followed by power steering being disabled mid-drive)
  • Park Assist Unavailable
  • Lane Departure Avoidance features unavailable
  • Regenerative braking temporarily reduced
  • Automatic Emergency Braking reduced
  • Stability control disabled
  • Traction control disabled
Autopilot disables as well and sometimes at red "P" displays on the upper right saying something like "Parking Brake Disabled".

This began ~2-3 years ago, and I have had multiple previous visits at Tesla during which they said they couldn't reproduce the errors or that the issues were resolved, but they have inevitably recurred. The issue used to be rare but now happens much more commonly, coming back in full force after the most recent update (which I tried to avoid but self-installed anyways). Now the power steering drops out while mid-drive about 7 out of 8 times when I take it out, which has put me in some dangerous spots. Even more confusing, I recently had a mobile visit where the mobile technician also noticed these problems and thought it might be the 12V battery, but he then sent me the following text afterwards:

He's since set me up with another in person visit which I will have later today. I have a sneaking suspicion that they will say the same thing -- that the errors aren't able to be reproduced or that the issue is fixed only to have it recur after I pay the bill and go home. Possibly related is that the coolant pump stays on after I park even when not using AC. I had a bad hit and run in 2018 where I was struck severely on the front left while I was driving, wonder if this is a residual issue though I don't think I could prove this to insurance ($35k worth of damage at the time). The mobile technician thought it might be a 12V battery issue, but he is really confused as to why the errors aren't registering with Tesla's main server. Also, replacing the 12V doesn't come up as one of the error messages (though perhaps it wouldn't if related to one of its connections and not the battery itself)?

I've put a pretty penny into the diagnostic work up trying to figure this one out and am dreading my visit with Tesla Service later today as being another Groundhog's day. Have any of you had similar issues or any thoughts as far as troubleshooting?

Any advice would be sincerely appreciated!
Strongly recommend a visit to Safercar.gov where you really must file an alert with NHTSA. Perhaps it will save a few lives.

We have had more than a dozen MS’s since 2013 and more than one spontaneously lost its power steering: the steering effort is so extreme as to likely cause many drivers to think the steering had “locked up.” Always intermittent, Tesla’s repairs were often just guesses that had no real impact on the issue, an issue that could easily lead to a major accident.

As for your car?

Given your many troubles, and the great dangers you have repeatedly submitted yourself to, I highly suggest you ask Tesla to make you a VERY generous trade-in offer. You get a new Tesla, with the expectation that your old car will become part of Tesla’s service Ranger fleet—maybe it’ll finally be fixed correctly.

Don’t wait until you lose power steering again….
 
  • Helpful
Reactions: Watts_Up
As an aside, on the most recent example, we just traded the 2017/8 (I think) MS Perf with this issue into Tesla after the event occurred a second time, but only after they had diagnosed a potential issue with a wiring harness (or perhaps it was just a guess on their part).

While the harness was on order to arrive for a scheduled service visit, we traded it in. So it was ON SITE at the Dallas Service Center for the next day's previously scheduled service/repair appointment. Very much NOT wanting to dump a potential safety issue on the next owner, we left MULTIPLE notes in and on the car to advise that the car had a scheduled service repair for a major safety issue, AND I visited a service advisor to tell him the car was on site and ready for the repair.

Afterwards I checked with sources to monitor the car's progress. Of course, the repair was never accomplished.

I visited the service manager at the Dallas Service Center a few weeks later soley to explain my concern about the "ticking time bomb" on Tesla's hands. He said, "I'll take care of it."

He didn't.

Weeks later I found out it had been sold, but not yet delivered. Fearing for the life and safety of some poor unsuspecting Tesla buyer, I ended up FedExing a letter to someone involved with safety at Tesla HQ, advising of the potential threat of a major accident from this MS Performance's intermittent hazard. Their office called me back the next day to advise that the sale was, finally, "On Hold" pending the repair.

Sometimes I wonder how Tesla, as an organization, can be so brilliant, yet so amazingly stupid, at the same time . . . .

As you well know, loss of the EPAS system can make the car effectively a missile so do not accept the status quo.

Trade it in to Tesla; don't risk your life with this ongoing safety issue. BUT you may have to stay on them to see if they just re-market it as a used car, or if they actually fix the problem . . . .
 

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