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In terms of a "long time"... let's say you have this issue and have the luxury of pulling the fuse and leaving the car overnight.... Would that be enough time for the TCAM backup battery to sufficiently discharge and reset when reconnecting the fuse?

Or are we talking dayS with the fuse out?
 

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Thanks. I assume the back up battery is re-chargeable, and gets it’s supply from the primary 12v car battery? So, if disconnected from the primary would, eventually, dissipate…but who knows how long that might take.…so probably not good solution to remove the fuse…just easier.
Yes, it's a rechargable one. If the charge status is low you get a ecall warning on the dash (I think the threshold is 40% based on a TSB I read a while ago). It recharges while driving, and will take a few hours. There should be no need to replace it even if it has drained completely.

In any case, the only situation I'm aware of that you need to disconnect it is if the keys aren't recognised and you want to power cycle the TCAM to fix this.

I suppose it's not impossible for the backup battery to also be completely flat, in which case merely disconnecting the 12V should do the trick to get the keys working, probably worth disconnecting 12V briefly and checking if the keys work before disconnecting 12V again and going ahead with the massive PITA of unplugging the back up battery.

There is no reason to replace the back up battery if it drained, it's similar to cell phone batteries so perfectly happy to discharge fully more than a few times. Volvo Assistance in the UK carry pre-charged ones and will swap them out when 12V has drained as that causes the TCAM to tap on that and drain it too very quickly, but the only reason they do that is to be able to clear all error messages before leaving the site. It wouldn't be good customer service to tell someone yeah you'll have an ecall warning error for the next 4-5 hours of driving and it's normal.
 

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In terms of a "long time"... let's say you have this issue and have the luxury of pulling the fuse and leaving the car overnight.... Would that be enough time for the TCAM backup battery to sufficiently discharge and reset when reconnecting the fuse?

Or are we talking dayS with the fuse out?
That's a good point, waiting for it to discharge might be an option if you've got the time and probably less annoying than having to reach in and disconnect it.

Without electrical diagrams (or trying it!) I can't be 100% percent that merely removing the TCAM fuse will do the trick, but if you don't mind disconnecting 12V which is easy and wait for it to drain it'll do the same thing.

My plan was for the next time I have this issue to just pull the fuse and disconnect the backup battery instead of doing the 12V disconnect, to test if this is sufficient. If it is I'll update my guide.

Hard to say how long it'll take for it to drain though, it's a 2000mAh/7.2Wh Li-ion one, similar to a small phone like the iPhone SE, so if it's just keeping the radios on at standby it might be a couple of days...
 

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Yes, it's a rechargable one. If the charge status is low you get a ecall warning on the dash (I think the threshold is 40% based on a TSB I read a while ago). It recharges while driving, and will take a few hours. There should be no need to replace it even if it has drained completely.

In any case, the only situation I'm aware of that you need to disconnect it is if the keys aren't recognised and you want to power cycle the TCAM to fix this.

I suppose it's not impossible for the backup battery to also be completely flat, in which case merely disconnecting the 12V should do the trick to get the keys working, probably worth disconnecting 12V briefly and checking if the keys work before disconnecting 12V again and going ahead with the massive PITA of unplugging the back up battery.

There is no reason to replace the back up battery if it drained, it's similar to cell phone batteries so perfectly happy to discharge fully more than a few times. Volvo Assistance in the UK carry pre-charged ones and will swap them out when 12V has drained as that causes the TCAM to tap on that and drain it too very quickly, but the only reason they do that is to be able to clear all error messages before leaving the site. It wouldn't be good customer service to tell someone yeah you'll have an ecall warning error for the next 4-5 hours of driving and it's normal.

I am glad you guys are regulars here. I’m learning a lot about a car I just got a few months ago….so if/when this happens, I won’t freak out and know what to do. 👍
 

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Discussion Starter · #26 ·
In terms of a "long time"... let's say you have this issue and have the luxury of pulling the fuse and leaving the car overnight.... Would that be enough time for the TCAM backup battery to sufficiently discharge and reset when reconnecting the fuse?

Or are we talking dayS with the fuse out?
You may get lucky! I pulled Fuse 26 and Fuse 27, left them out 5 minutes, and put them back in. A few minutes later, my TCAM was back online and working. I pulled the rear carpet just to be ready for that if needed, but this time I didn't need to disconnect the backup battery. Pulling the carpet/trim using kkonstan's method is really easy. Getting to the BUB with the carpet back is still probably a bit tricky. You can pull the fuses without extra tools vs. unhooking the main 12V battery. I think all you need is maybe a screwdriver to pop the backup battery loose.
 

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You may get lucky! I pulled Fuse 26 and Fuse 27, left them out 5 minutes, and put them back in. A few minutes later, my TCAM was back online and working. I pulled the rear carpet just to be ready for that if needed, but this time I didn't need to disconnect the backup battery. Pulling the carpet/trim using kkonstan's method is really easy. Getting to the BUB with the carpet back is still probably a bit tricky. You can pull the fuses without extra tools vs. unhooking the main 12V battery. I think all you need is maybe a screwdriver to pop the backup battery loose.
glad you got sorted it seems. Are you on 2.2 con CarPlay?

I wonder if they’re doing some server side adjustments that are kicking off TCAM weirdness.
in our nonPP car had an episode of GPS going out, LTE and key recognition being intact. Let the car sit and think through things for about 20-30 min. Then drove it around for another errand and during that drive the GPS came back.

all seems well now knock on wood
 

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You may get lucky! I pulled Fuse 26 and Fuse 27, left them out 5 minutes, and put them back in. A few minutes later, my TCAM was back online and working. I pulled the rear carpet just to be ready for that if needed, but this time I didn't need to disconnect the backup battery. Pulling the carpet/trim using kkonstan's method is really easy. Getting to the BUB with the carpet back is still probably a bit tricky. You can pull the fuses without extra tools vs. unhooking the main 12V battery. I think all you need is maybe a screwdriver to pop the backup battery loose.
Awesome - congrats!! So both fuses (26 and 27) need to be pulled ?
 

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Discussion Starter · #29 ·
2.2 with CarPlay, but I don't use CarPlay. I'm an Android user that wants Android Auto. If I had Android Auto today, I could have used my phone to do things while my TCAM was down.

I can't think of anything special last night or this morning that may have caused the TCAM failure.
 

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I'm just guessing here, but the two fuse pull (26 and 27) are likely equivalent to a TCAM "soft reset" like the demister option except maybe more dependable than the latter. 12v disconnect and BUB disconnect is more of a "hard reset" - a full power down and recycle. Sort of like a reboot of a PC vs. a full power cycle. There are situations where the full power cycle is the only way to recover a component. Why I suggest this it that the BUB is there to maintain some state on the TCAM that is stored in volatile memory rather than some sort of non-volatile storage. A full power down would clear any persistent state storage the BUB is providing power to.

But I could be wrong. It's happened before. Just ask my wife and she can gleefully recite every time I've been wrong in great detail. 😒
 

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Tested the car a bit more. GPS outrage came back and this time Connect wasn’t lit up and SOS flashed red a bit then went back to solid white
Did an infotainment tablet reset. GPS stayed out and now the maps just showed a zoomed out view of all of N America and had LTE filled triangle with a little x indicating no connectivity. Held front defrost down for about 20s. SOS went back to flashing red. I let go of front defrost. Then after a minute all came back, including the last track that was playing (Enter Sandman - perhaps appropriate!!).

perhaps tinfoil hat thinking but I strongly suspect backend things kicking sensitive TCAMs into a loop.
 
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I had the issue about a month. Similar situation (4 hours to nearest space . . . about 1 hour to a Volvo dealership that told me it did Polestar service before I bought the car (in March), but no one seemed to treat the vehicle going there for the issue as a legitimate option) and after too long on various help calls I went ahead and did the the hard reset myself. The 12v was trivial. The TCAM back-up battery was much more of a pain than I was expecting. I assume it will be easier the second time. :)

Good luck.
 

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I've had my car for 6 months and just experienced my first total TCAM failure. I've had problems before that were solved with a defrost button reset, but this is the hard fail with the eCall service message. Keys don't work, GPS doesn't work, network is obviously down, etc..

Customer service says they will tow it from Salt Lake City to Denver (~500 miles) and provide me with a rental car. I'm wondering if I should let them do that, or if I should try the TCAM battery removal reset? I don't like the idea of getting a crappy rental car and being out of my car for an indeterminate amount of time. I would be more likely to let them take it if they would also fix my loud AC compressor noise and install my tailgate kick sensor at the same time, but I have zero faith they would do either of those things.

What would you do?
Other than service being 500 miles away I brought my car in and waited a couple of hours for them to do the reset. You should get your car back fairly quickly.
 

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Thanks R/T Turbo. Pulling out fuse #26 & 27 under the front passenger fuse box fixed most of my tcam issues. It needed the overnight for se-out (3rd try) instead of short 5 or 10 minutes.
My eCall failure warning is still on. A tech mentioned that my tcam batt was low and would need at least 45% to reset. I will try the front defrost reset myself after driving and charging up my car first.
Count back from the last empty fuse slot as 32.
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So that might be helpful then - by pulling the fuses then waiting overnight that would seem to be enough time to drain the BUB and completely reset the TCAM. And because the BUB was completely drained then I would expect the eCall failure to last for a while until, as the tech said, the BUB can recovered enough charge. Personally I would disconnect the BUB and the 12V per the process described in the sticky post and retain whatever charge is in the BUB and have the TCAM reset happen quickly. But at least here's another option for those who have some time and patience and don't want to fool around with digging around under the trim in the trunk/boot. Thanks for the info!
 

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Discussion Starter · #37 · (Edited)
I pulled those fuses and waited 5 minutes to fix my TCAM problem. I understand that won't work for everyone and some people will also need to disconnect the BUB. I would pull the fuses and disconnect the BUB vs. leaving the fuses out all night. It seems like you may create more problems by draining the BUB.

I think pulling the fuses is easier than disconnecting the 12V battery.
 

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All I can say is pulling the fuses would be the equivalent of disconnecting the 12V battery only. That can solve some problems as you have experienced, but there are many instances here on the forums and on the FB group where only a complete power down of the TCAM will sort the issue (even if only temporarily) - this can't happen as long as the BUB is still connected and has a charge. It's the whole reason it is there after all - to maintain some state in the TCAM unit.
 
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