Model S

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Multiple Failed Front DU on 2017 Model S 90D (Less than 5k miles)

edited February 2018 in Model S
Hey guys,

So, my wife and I have had two bad experiences with our 2017 Model S 90D and have had it only since the first week of July and have put around 5k miles on it.

First issue was warnings on the dash that something was wrong, needed service, and power was reduced (Tesla termed it 'limp mode') midway on a road trip from NYC to Boston for a weekend. We were advised to either 1) Call for a tow or 2) try to get it to our home dealership in Brooklyn, since we were over 100 miles away from home and the nearest dealership was in Connecticut where it would be serviced.

It took 13 days, but eventually had the front Drive Unit replaced because the warnings were due to a failing front Drive Unit.

This past weekend, we were on our way back home (from Connecticut again, maybe we should avoid the state) and halfway across the Henry Hudson bridge when all of a sudden the car lurched forward and 6 error messages appeared on the screen, all at once.

Park Assist Unavailable
12V Power Low - Car May Shut Down Unexpectedly
Unable to Drive - PULL OVER SAFELY
Car Needs Service - Car May Not Restart
Car Needs Service - Unable To Start Car
Car Needs Service - Contact Tesla Service

Thankfully we had enough speed that we were able coast down the bridge and pull over. In addition, on the dash, PRND were all marked red. We called Tesla Roadside, and while on the phone with them, the 12V auxiliary battery shut down and everything went black. 3 hours and 3 tow trucks later, as no one could figure a way to get it into tow mode, we finally found one that was willing to flat bed it (I believe he dragged it, wheels locked) to the nearest dealership in Paramus, NJ. Super fun.

Anyways, just got a text from Tesla saying "we have ordered a new front DU for your model S, we'll update you when we have an ETA".

My question is, shouldn't they be looking into a root cause for our car causing a failing front DU warning and then, after replacement another one that catastrophically failed and left us stranded? Obviously something is causing these to fail on OUR car with < 5k miles and there might be something deeper in this vehicle that's causing them to fail so often?

Anyone else have multiple front DU failures on a (relatively) new Model S? The first replacement took 13 days, if this one takes nearly as long, we're approaching the 30-day lemon law in NY. Should we be talking to Tesla about a possible replacement? We are really concerned with the reliability of this particular vehicle and will have a hard time trusting it frmo now on.


  • edited November -1
    I'm on my second Model S (P100D). Had it since November 2016... 10,200 miles and no problems...
  • edited November -1
    You are the first I recall with this problem, so I doubt they will look for root cause.

    They discontinued the 90D - I didn't know they were still selling them in July 2017. You must have gotten one of the last ones.

    Here is the info about the lemon law:
  • edited February 2018
    Yes, we actually got it on June 30, 2017, they took $10k off as they were trying to move the last bits of 90D inventory out for 100D's.

    Seeing as this car is the first you've heard of, wouldn't it make sense to look at the root cause of the issue, instead of throwing another Front DU at it, only to have it fail again in another 2-3 months?
  • edited February 2018
    Wish I could edit posts... What I mean by "looking at the root cause" is looking at the root cause on OUR vehicle.

    I meant to say that I'm pretty sure the Front DUs are fine, but there's something deeper in this vehicle that's causing perfectly-good Front DUs to fail successively and that they should be trying to figure out what that is, instead of replacing the DU again that'll like fail again due to whatever is causing them to fail.
  • edited November -1
    They do look for the root cause by sending the failed unit to Fremont for evaluation and not inconvenience you with troubleshooting.
  • edited November -1
    While driving you got this message?

    Car Needs Service - Unable To Start Car

  • edited February 2018
    But do they do further evaluation on the vehicle? It seems to me that something in the vehicle itself is sabotaging the units and will continue to do so.

    Yes, I took a picture of the screen once we had stopped. I think it's because whatever happened shut the car 'off', but we were still moving/rolling and my wife was trying to press the accelerator and sitting in the seat and the car tried to turn itself back on but was unable to? Your guess is as good as mine!
  • edited February 2018
    Just let them fix it. Micro managing does not help.
  • edited November -1
    If something is causing this issue, it may be found in the logs. That's probably why they had it so long the first time. Drive units take 3 days to replace in my experience. That includes shipping.
  • edited November -1
    @jawatkin - sorry you are having troubles. That doesn’t sound like a DU issue, based on wha lt people have reported. If it is, the SC should be able to tell you why the DU is giving you those seemingly random unrelated errors. Sounds more related to a data bus or electrical junction type of issue, if I were to guess.
  • edited February 2018
    Wha it -> what
  • edited November -1
    This sounds like the spate of strandings that occurred early in the P85D production run - exact symptoms you describe happened on my car and others. It was due to an OTA download of flawed code to implement the motor sleep mode on dual motor cars. There was a temporary workaround (turn off the power saving mode), and a very quick OTA fix. However, all of those cars were able to restart after stopping (in my case in the middle of a high speed highway), so different from how your event ended in that respect.
  • edited February 2018
    @tes-s: I did. Now it's broken again, less than 3 months later. Trying to avoid a third failure in another 2-3 months.

    @SbMD: Last I heard from the SC was they'd ordered us a new replacement Front DU, will ask them about possible "upstream" issues like the data bus and electrical junction, thanks!

    @Pungoteague_Dave: Hadn't heard of this (new to the community). Did the issue with the P85Ds end up in HW replacement for any of the affected models, or just a firmware fix?
  • edited February 2018
    I have a mid 2016 MS90D. I had a similar experience with sudden drive unit reduced torque quickly followed by pull over safely as I was stopping at a stop light, ending up with the car stopped, “dead stick” (red PRND indicator), followed by a discussion with road side assistance and my car getting towed. I did not experience the 12V messages and total electrical shutdown, so my car was able to be put into tow mode.

    My root cause turned out to be a flawed diagnostic, deemed by engineering to be a “rare software bug” (those are the exact words from my service invoice).

    The most important thing out of this was the local service guys telling me that next time to fully exit the car, let it totally shut down, and then unlock and get back in. That triggers the diagnostic to run again, which in my case would clear the error and allow me to drive away normally. That never happened at the time as I called roadside assistance from inside the car, and while I got out waiting for the tow truck, had left my key fob inside the car not wanting to forget to give it to the tow truck driver.

    I’m not sure this would have helped @jawatkin as sounds like something more in his case with the 12V battery failure, but something I’ll remember to try if I ever experience another case where car throws a drive unit error an not able to go back into gear.
  • edited November -1
    @jawatkin "@Pungoteague_Dave: Hadn't heard of this (new to the community). Did the issue with the P85Ds end up in HW replacement for any of the affected models, or just a firmware fix?"

    Pure firmware, and fast because it was caused by a poorly tested OTA update - and was fixed by another OTA upgrade - IIRC within a week or two. Meanwhile there was a safe way to drive the car for those in the know, although it wasn't widely distributed information.
  • edited November 2018
    Well...hate to put the fear into all of you optimistic Tesla owners with your new drive units 2014 S85 had a drive unit failure at 40,000 miles. When they replaced it, the tech told me that there was a defect in the early units that was caused by the pressing machine being located on the second floor of the factory. When the machine was pressing the units, the floor was flexing just enough to cause a problem but not enough for them to notice. They have since re-located it to a ground level floor so this new drive unit will last forever. Apparently "forever" is about 57,000 miles because today, my drive unit was replaced again at 97,000 miles. This time it was due to coolant leaking into the unit and causing corrosion. I mentioned what the tech had told me before about it "lasting forever" and this tech said, "I wouldn't ever say that. We are dealing with new technology and there will always be problems." So, I said, "so what you are saying is that I should get rid of the car before I get to 8 years?", he did not answer but I got the idea that he was agreeing with that. Now, I am deciding what to do. I had planned to keep this car for 10+ years and also get a second one but now, I am a little worried. My concern is that the car will become instantly worthless the day it turns 8.
  • edited November 2018
    My drive unit has 150,000 miles on it.
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