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2012 Model S - Limp mode - BMS_w172 (Vehicle may not restart) , BMS_u008 (Acceleration and top speed reduced)

Tripple_T

Cincinnati Member
May 20, 2015
160
103
Cincinnati, OH
Hello All,

Recently had my model S go into limp mode; BMS_w172 (Vehicle may not restart) , BMS_u008 (Acceleration and top speed reduced).

This happened at the same time as the 12v battery needing to be replaced. We took the car to a service center and had the battery replaced. All seamed normal for a day. Then the messages came back. Tesla quoted to replace the battery heater. I opted to replace that myself. All went fine with the replacement and I could see the heater working (based on kw usage). However, the error messages did not go away.

I took the car to a supercharger and as I went to plug into the charger the car errored saying "Voltage Low" and "Unable to start car". I pulled the 12v and fire disconnect and got the car to start back up and it was able to charge to 90%. Seamed like the battery was just fine when charging. Got the car home and was able to charge as well.

From research of these errors and the behavior I'm thinking the HC contractors are worn/corroded.

What are the thoughts of the hive brain? I'm guessing this wont be cheap to have Tesla do. Any thoughts on the cost/repair?

Tucker
 
I posted this in another thread about battery heater woes…. I wonder if there is some software glitch around supercharging that is triggering fals battery heater problems. Could you tell if the battery heater you replaced was actually broken?

So my 2016 model S gave the error code Bms_w035 code just as I arrived and parked at a supercharger. Since I was navigating to the supercharger, it said it was preconditionping for faster charging. the car did supercharge at 100+kw so the battery was warm. the First message triggered a service required message. When I started the car after supercharging, it threw the additional codes bms_w172 and bms_u008. The dreaded ”limp mode” and “car may not restart” mesages. I scheduled service the next day and got an appointment for 3 weeks later. I Drove the car in limp mode a few times and did a power down restart but limp mode and may not restart remained. It looked like they did a remote diagnosis when they scheduled the appointment and they predicted the expected battery heater needs replacing and quoted $658 to fix it since I am out of warranty. I dropped the car off and got a model 3 performance loaner. It took them another week to actually look at the car. When they cleared the limp/may not restart codes it no longer reported any trouble. They ran diagnostics and found nothing. They called and asked permission to do additional debug for a 1 hour service fee. I reluctantly said ok, and they did additional testing and thermal cycling. They couldn’t find any problem. In the end quite a big hassle for what seemed in my case to be a software glitch. In the end I wished I had gotten them to clear the limp code remotely and just seen if the code for the battery heater would reappear. YMMV.
 
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Tripple_T

Cincinnati Member
May 20, 2015
160
103
Cincinnati, OH
So I don't think their was anything wrong with the old heater but I didn't do any test. I still have that heater. I could check the resistance. There really isn't much to go bad in those. The weather is getting colder so I thought maybe it was related. It all started when my 12v battery needed to be replaced. I'm very suspect that something is actually wrong.
 
Did you get the bms_w035 message originally?

So I'm in limp mode again. Same thing as before. Set destination to supercharger, drove there. Battery heater clearly working as it is cold here, 35 degrees and the battery heated up by the time I made it to the supercharger. I could tell both by the regen going to fully available and using tesla-spy to see the battery temperature go from 50 to 70 degrees. As I parked at the supercharger, it gave the bms_w035 code and "may not restart" followed by the other two limp mode codes. Supercharged at over 100kw without a hitch. Car drives in limp mode fine.

Does pulling the 12v clear limp mode? Does pulling the HV loop?
 
Left my car at service.Was scared to drive it as I had a broken suspension a couple of months ago - PTSD.
WhatsApp Image 2021-12-15 at 10.23.53 AM.jpeg
WhatsApp Image 2021-12-15 at 10.22.51 AM.jpeg
 

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