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

[Tripple_T]

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

 

[adspguy]

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.

 

[Tripple_T]

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.

 

[adspguy]

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?

 

[Tripple_T]

I had to pull the 12v and HV Loop to get the car to start. I got a message saying the car would not start. Pulling HV and 12v cleared the hard message but didn't clear the soft/limp messages.

 

[Kaveman]

You could try the "Change Wheels" reboot. See if it resets things for you?
My $.02
Kaveman

 

[Tripple_T]

Yep. That is a great trick. I tried it a few time and it didn't clear the messages.

 

[SMSMD]

Left my car at service.Was scared to drive it as I had a broken suspension a couple of months ago - PTSD.

 

[GeorgeCM]

Hi,
Do you remember what was the issue ? I have exactly the same error. Have they replaced the contactors ?

 

[Starman]

I've got the same issue. Tesla replaced the 12v and battery heater. It worked as normal for a couple drives and now my cautions are back, Acceleration and top speed reduced with Vehicle may not restart as well.

 

[maximizese]

When I had the two alerts, plus "Regenerative braking system disabled" Tesla Service replaced my drive unit, 12V battery, HVAC drain hose, pyro fuse, and HV contactors just before the warranty ran out. I'm not sure which component triggered which warning, but I did have a low coolant warning months early that Tesla looked into it. Knowing what I see now, I'm wondering if my drive unit had coolant ingress into the inverter that some with way more knowledge than me have been noticing on 2012-2015 and a few 2020 Model S vehicles. Apparently there is a seal that seems to fail.

 

[Starman]

I'm still in service with mine but it looks like they're waiting for parts to replace the rear drive unit.

 

[Ewiz]

I have the same 2 warnings. Tesla is starting with a rear drive u it on my 2015 S 85D. The rear unit was whining/ milling as well. Stay tuned

 

[Ewiz]

I have the same 2 warnings. Tesla is starting with a rear drive u it on my 2015 S 85D. The rear unit was whining/ milling as well. Stay tuned

Same here 15 S 85D. They started with the RDU didn’t fix it but now I have a new clunk in rear! So frekin annoying.

Electric coolant heater ended up being the problem with my limp mode

 

[Ewiz]

Same here 15 S 85D. They started with the RDU didn’t fix it but now I have a new clunk in rear! So frekin annoying.

Electric coolant heater ended up being the problem with my limp mode

I am trying to escalate but doesn’t seem to go anywhere. My FDU has a super high pitch milling noise they won’t fix

 

[Chan Meas]

Left my car at service.Was scared to drive it as I had a broken suspension a couple of months ago - PTSD.
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I just got this notification and got scared. I dropped it off at the service center in Fresno. Awaiting a price quote without warranty. I am hoping it is not too expensive to fix.

 

[andersonbsc]

I just got this notification and got scared. I dropped it off at the service center in Fresno. Awaiting a price quote without warranty. I am hoping it is not too expensive to fix.

Anything?

 

[Chan Meas]

Anything?

Rear drive unit went out. $7820 to replace. Luckily for me, the unit was under a 4 year 50k mile warranty. I didn't pay anything out of pocket. However, this is the 2nd drive unit I have replaced in 2 years. Not sure what the quality of these units are. New drive units should last at least 10 years or longer, right?

 

[NewbyMaybe]

Same here. First replacement took several weeks to find, probably rush jobs at that point in the market. Last year's replacement was like new according to the tech, found in a few weeks.

 

[andersonbsc]

Mine