Advice: BMS_w035 - battery coolant heater? Causing other alert codes too.

[dwbv]

2015 P85D, 15k miles, warranty died on 3/31/23, bought it 3 weeks ago, in my possession for only 1 week, driven less than 20 miles.

Well, I suppose this is part of owning a Tesla. One week of physical ownership and here we go. The first 6 miles of driving was fine. Took it out this morning for another drive and on the way back home about a mile from home, I got the BMS_w035 alert. No hard driving and no higher than 65mph max. It drove fine all the way back home. Parked it and plugged in the charger. Shortly thereafter, checking up on the car also showed BMS_u016, then BMS_w172 showed up followed by BMS_u008.

Looked up many threads on this issue on here and it seems to be the battery coolant heater? It's been cold in my garage but nowhere near the sub-zero F degrees. Supposedly the 12v battery? I tore the front apart and looked at the battery. The negative terminal was a bit loose so I tightened that up. Powered down the car and powered it back up after 2 minutes as recommended. Same alerts remain.

I did take the car out and was able to drive it without issue albeit no regen and only under-100kW. Everything else seems to work just fine.

Is there anything I can do? I'm tempted to pull the 12v and the fireman's loop for a hard reboot since I've got the front wide open but I'm thinking that won't do anything. I'm 2.5 hours away from the closest SC. Can you replace the battery coolant heater yourself? Easy DIY?

I might just let the car sit for now and see if it fixes itself when the weather warms up (wishful thinking)? Any advice is appreciated. I'm guessing it's gonna go to the SC.

 

[NewbyMaybe]

Start by checking and trickle charging the 12v.

 

[dwbv]

Start by checking and trickle charging the 12v.

Should I disconnect the 12v to do this? I can check voltage and just charge it to full? I've got a CTEK 7002 battery charger that is collecting dust that I can put on it.

Thanks in advance!

 

[hydro]

service.tesla.com will help you sign-up(it's)free and browse the service manual among other things

 

[dwbv]

service.tesla.com will help you sign-up(it's)free and browse the service manual among other things

I'll check this out. Thank you!

 

[dwbv]

@NewbyMaybe I measured 12.6-7 volts which indicates the battery is fine. Looks like the previous owner put in a deep cycle battery unless this is the factory oem battery? Perhaps I should take another voltage reading with the battery disconnected from the car?

C & D Technologies | Deep Cycle Series DCS AGM Battery

 

[KalJoMoS]

That battery seems to be quite fresh, obviously from last year (there is a stamp on it 0922A). This is the OEM one, not to worry. But do keep it charged if you are not able to use the car.
Your situation might be similat to this, worth to read all the discussion. Mine was the battery coolant heater failure but I had few extra errors on the screen. Yours might be just the PTC heater as your car is still drivable. Obviously you have read all the posts but there are several discussions about how to change out or even fix the PTC heater. The screen of errors of mine is here:

 

[NewbyMaybe]

12's are okay if the car is asleep and not maintaining it. If the car is awake then it should be 13's

 

[dwbv]

12's are okay if the car is asleep and not maintaining it. If the car is awake then it should be 13's

I'm getting 14.5-6 volts when the car is awake. I think this is within the normal ranges. Looks like it's not the 12v battery.

 

[dwbv]

That battery seems to be quite fresh, obviously from last year (there is a stamp on it 0922A). This is the OEM one, not to worry. But do keep it charged if you are not able to use the car.

The car is driveable. It just won't let me use more than 100kW plus no regen. I took it out for a drive already and was able to get up to about 45mph easily and hold that speed with what looks almost like about 20-30kW power. I can't say how it would do on the highway and not interested in finding out at the moment.

Your situation might be similat to this, worth to read all the discussion. Mine was the battery coolant heater failure but I had few extra errors on the screen. Yours might be just the PTC heater as your car is still drivable. Obviously you have read all the posts but there are several discussions about how to change out or even fix the PTC heater. The screen of errors of mine is here:

I will look more into this PTC heater. I don't know if this matters or not but my heater for the cabin works. I can set my HVAC to 80F and it will blow mildly hot air within minutes.

 

[Doanster1]

Most likely the battery coolant heater vs PTC. I had mine fail around 50k miles IIRC. Have the SC do remote diag to confirm. Only a few hundred for them to replace. Easy DIY with hose clamps if you’re up for it. Mine was replaced under warranty.

 

[dwbv]

So I saw this video:

Decided to give this a go to test if the coolant heater was working... sure enough, after over an hour of waiting and hearing the coolant circulation whining, the coolant lines under the frunk were very warm to the touch and the screen was showing that Insane+ mode was ready and the battery is up to temperature. Does this mean the coolant heater is working?

I then decided to go out for a drive... 12 miles worth. The car continued to stay in limp mode and never allowing me to go past 100kW or regen. All the while I was driving, I had the HVAC to 75F and warm/hot air was blowing through the vents into the cabin. Does this mean the PTC heater is working?

Despite being in limp mode, I was able to get up to 65MPH and maintain that speed with a consistent 30kW power draw. The acceleration is definitely nerfed but the car is still very drivable in day-to-day traffic.

At this point I'm thinking either the coolant heater or the PTC heater are not working up to some par-level and throwing errors? Therefore this causes the car to go into limp mode and stay there indefinitely. I will do a HV and 12v disconnect tomorrow to do a deep level reboot... then I'll reach out to the SC for diagnostic help.

No other issues that I can tell with the car otherwise. It continues to charge without any issue.

 

[dwbv]

Most likely the battery coolant heater vs PTC. I had mine fail around 50k miles IIRC. Have the SC do remote diag to confirm. Only a few hundred for them to replace. Easy DIY with hose clamps if you’re up for it. Mine was replaced under warranty.

What do you mean "heater vs PTC"... do these two work against/for each other and need each other? I will do a deep reboot tomorrow and then reach out to the SC. The closest SC to me is about 3 hours away so if I can just buy this heater and put it in myself, that would be preferable. Any DIY instructions and/or videos anywhere on how to do the coolant heater? If I can do a timing belt, I should be able to do this.

Saw some videos on the PTC and looks like the passenger side dash has to be ripped out to get to it?!

 

[KalJoMoS]

Yes, the PTC heater is under the panels on passenger side but as you have tested it might not be the issue. If you have confirmed yourself that the battery heater is also working (can you turn the HVAC on remotely in your app?) then it might not need to be changed as well. If the remote heating prior your driving does eliminates the restrictions on regen then you’re good.
There are few items that run on the HVIL and if one of the items are having a failure then you will end up with corresponding warnings. On the front DC-DC converter there are HV connection to PTC heater, battery coolant heater and HVAC compressor. That limp mode limitation on your can might be failure of one of them or it’s completely different issue and it might be a failure of the large DriveUnit (was your car dual motor version?).
What warnings do you see under the service hidden mode (you need to enter that menu on the MCU under service section)? You might get correct reboot with the Fireman's/12V disconnection but do look up that service hidden mode. Here is one document describing the procedure Tesla is using for HVIL errors.
edit:
I just recently had to change one of the low voltage cooling pumps as the preheating did not operated as should. And I needed to change the battery heater last November.

 

[dwbv]

Yes, the PTC heater is under the panels on passenger side but as you have tested it might not be the issue. If you have confirmed yourself that the battery heater is also working (can you turn the HVAC on remotely in your app?)

Yes, I'm able to turn on the heat from my app; notice the temp difference inside car vs outside

then it might not need to be changed as well. If the remote heating prior your driving does eliminates the restrictions on regen then you’re good.

Regen never came back despite heating up the HV for insane+ mode. Here's what it was last night after my 12-mile drive:

There are few items that run on the HVIL and if one of the items are having a failure then you will end up with corresponding warnings. On the front DC-DC converter there are HV connection to PTC heater, battery coolant heater and HVAC compressor. That limp mode limitation on your can might be failure of one of them or it’s completely different issue and it might be a failure of the large DriveUnit (was your car dual motor version?).

Yes, dual motor; 2015 P85D.

What warnings do you see under the service hidden mode (you need to enter that menu on the MCU under service section)? You might get correct reboot with the Fireman's/12V disconnection but do look up that service hidden mode. Here is one document describing the procedure Tesla is using for HVIL errors.
edit:
I just recently had to change one of the low voltage cooling pumps as the preheating did not operated as should. And I needed to change the battery heater last November.

I did glance at "service mode" last night but it wasn't showing anything too special than the errors I'm already seeing. That troubleshooting documenatation might be above my pay grade, hehe. That's some technical stuff. I'm sure I could learn it.

I will collect those service mode codes and post back. I will attempt the HV and 12v disconnect after work today and see what happens. Thereafter, I will request service from SC.

 

[wk057]

Those errors are related to high voltage isolation faults.

The main culprit tends to be the pack heater. You're stuck in limp mode because the car detected an isolation fault multiple times, so it won't reset that until the cause of the fault is rectified.

Suspects are usually the pack heater (most common), drive unit (coolant ingress on performance/large units), or the battery itself (moisture ingress).

Nothing to do with the 12V system, yet. If it's a progressing issue, it'll get to the point where the main contactors will refuse to close and then the 12V will completely die.

Only way to really narrow it down is to physically test the above components with a HV megaohm meter (not just the continuity check on cheap multimeters)... or have us or Tesla do it.

 

[BrownOuttaSpec]

^---- @wk057 knows his stuff and has his own repair business. Since you are new to this forum you might not know of him but he is 1,000% legit and and VERY knowledgeable. I started typing my response below before he responded:

When I got the BMS_w035 my battery heater died I didn't have the reduced acceleration bars that you have, so between that and the tests your performed I would say it is something else.

IF you want to do a "deep" level reboot easily you can change the wheels (19" -> 21") on the service menu and give it a few minutes and it will do a long reboot. I'm curious if the previous owner knew of a problem or it's REALLY bad timing. What happens if you do a full factory reset (Controls -> Settings -> Service & Reset -> Erase & Reset), do all the errors go away for a few hours/day or are they still there?

Either way, I guess it doesn't matter since you are 4 days out of warranty and you need it fixed. I would take it to Tesla service and ask them for some "goodwill" warranty replacement and cross yours fingers since it sounds to me like a battery/drive unit issue to me and don't forget “you get more flies with honey than with vinegar”. If they don't do it under warranty than I would suggest a 3rd party repair shop such as 057tech or Electrified Garage

 

[wk057]

It's worth pointing out that the issue can still be the pack heater even if the pack heater functions.

 

[dwbv]

Thank you so much to everyone for helping me out as a newbie-owner. I knew this day would come however I didn't expect it to be literally within days of new ownership. I guess might as well get it over with.

I did try the 12v and HV disconnect and that produce no results. I thought I would try to disconnect the plug from the DC-DC converter but apparently it's no longer in the passenger wheel well for my model year. Wasted a whole bunch of time on that for no reason. Anyone know where this is? I was reading that some people fixed this by reconnecting the coolant heater plug?

I've initiated contact with SC via the app. I guess I'll wait and see what happens. I'm super far away from 057Tech and Electrified Garage so I'll be patient with the car and Tesla for now.

IF you want to do a "deep" level reboot easily you can change the wheels (19" -> 21") on the service menu and give it a few minutes and it will do a long reboot. I'm curious if the previous owner knew of a problem or it's REALLY bad timing. What happens if you do a full factory reset (Controls -> Settings -> Service & Reset -> Erase & Reset), do all the errors go away for a few hours/day or are they still there?

I already attempted the wheel size change and it didn't make the errors go away. I'm afraid to do the factory reset as I'm reading some horror stories of things go wonky and such.

Either way, I guess it doesn't matter since you are 4 days out of warranty and you need it fixed. I would take it to Tesla service and ask them for some "goodwill" warranty replacement and cross yours fingers since it sounds to me like a battery/drive unit issue to me and don't forget “you get more flies with honey than with vinegar”. If they don't do it under warranty than I would suggest a 3rd party repair shop such as 057tech or Electrified Garage

I'm not expecting any handouts however I would be grateful if Tesla did that. Also, we're assuming it's battery and/or drive unit related.

Here's the service mode errors if anyone is interested (it's funny how it says "Performance may be restored on next drive" but it won't restore, dang it):

 

[dwbv]

@wk057 what is the best method to reach out to you? I want to make sure I have multiple options for repair once I hear back from SC. How does it normally work with clients whom are far away from you in regards to logistics?