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Nice, thanks for sharing. I've got all the equipment to do this, but the way I use the car it wouldn't benefit me very much. But good to know it is possible.
 

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Why do the jumper changes you recommend (Step 8) look different than the internal photographs of the telematics transceiver on the FCC web site?
 

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Nice work Yam!

Love old school board level hacks. Reminds me of the old DSS hacking days where you had to have (or learn) soldering skills to work the magic.
 

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Love this post. Great to see this kind of modification. Is it limited to certain carriers or would it work with diverse carriers like AT&T vs. VERIZON? My work for emergency management needs supplies us with cell phones and hotspots. I don't use the phone at all except for emergencies. The hotspot is always in my Bolt. The Bolt connects to it and I use it. Its unlimited with no throttling. My geographic area seems to favor Verizon so that's why I ask the above question. I could use the sim from either the phone or hotspot, but both are Verizon.
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As far as I understand, it should work with the SIM card of any operator that provides 4G LTE connection.
Can you please clarify exactly what to do in step 8? I am not sure I can see where the original 4 shunts are and where the new ones should be put (or from where to where to move the shunts).
Thanks
 

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Good stuff YAM, a few questions here, if you don't mind? I almost did this mod on my Chevy Spark EV, having located the same resistors. Not sure what site I published on, but it's the same idea.

Do you have a part number for that SIM card socket? There are a ton of them out there, and it would be good to know the pattern exactly so we could make sure we order the right one, or one that pins out to the equivalent.

Naturally, since this car is sold in many different international markets, a case could be made that as much of the telematics system as possible would have the same firmware load.... so?

Is there such a thing as Onstar in Ukraine? I'm guessing there is? Where is the car that you have originating from? Is it a Bolt or an Opel? I'm wondering if the firmware is different? I ask because the amount of bullshit we have had to deal with in the US with cell phones and carrier locks is nothing short of breathtaking, and cell companies have historically done everything in their power to abuse their customers and cripple hardware. Perhaps the barrier of having to rip the dashboard off was considered barrier enough in this case? But if you say it works with any carrier, then ****, let's give it a try. What have we got to lose? Onstar's bad service? 🤣

Any guesses on how the block diagram of this system looks? Does this board strictly supply a data connection and the head unit (and presumably Onstar) connects through it? It sort of makes sense since the head unit seems to indicate that it's connecting to the car's wifi hotspot when you start driving. Is Onstar's communication through VOIP maybe? Or a straight voice cell phone setup? My point in asking is, what does this break, if anything? If you put in a SIM that has voice service, does your car get a telephone number? That was at one point an Onstar service (why this is useful I couldn't possibly say) but I don't know if they're doing it now.

So what if we put in a data-only sim? Like in the US, the Google Fi data sims are a fabulous deal. But without voice or SMS, what might break? Voice, most people could care less about, but there's a feature that sends an SMS for charge events. I wonder if that comes directly from the car's SIM? It doesn't have a caller ID of a normal phone, so my guess is that it's coming from Onstar's own horrible backend somewhere, but I'm not so sure, since it seems far more reliable than the ONSTAR service, which, as of the past few weeks, has been DOWN a lot, sometimes for 12, and even 24 hours, with the website even being unable to get info from the car. Where in the chain that's happening is completely unknown, but it's garbage at the end of the day.

A FEW NOTES ON SMT (surface mount) REWORK FOR ANYBODY UNACCUSTOMED...

Suggestions to the people out there attempting this mod...Yam, you will probably agree, but please offer your knowledge...
These SMT resistors (jumpers, in this case) are TINY. They're gonna stick to your soldering iron if you can manage to get them off at all. Also, they're almost certainly ROHS solder, which melts at a higher temperature and is generally bitchier to work with, but not terrible by any means compared to classic tin/lead. It just doesn't flow as nicely and you can't mess around too long, since the heat will start to bother the board, solder mask, etc after a while. The good news is we can easily rework with leaded solder, and the odds of burning out a jumper from too much heat is low, and you can always jump it with solder or anything else you have laying around. FINE TWEEZERS are an important thing, along with PROPER ELECTRONICS FLUX. I use BGA flux for pretty much everything. It's expensive, but you use so little of it that it usually goes bad before you use it up. But the results are worth it. Use what you like, but flux cored solder WON'T CUT IT. Trust me. You need additional flux. Next up is the actual heat source. A soldering iron is technically possible to use, and you can get fine results, but using a cheap hot air rework blower is going to be way easier. Flux the whole mess, old pads and new, then heat it. Lift the resistor off and place it on the new pads, which will probably be melted perfectly. Watch the solder flow, add more if needed, and repeat. The SIM socket can probably be put on with a very fine tip soldering iron, the flux, and very thin solder. Suffice to say, this isn't beginner level soldering, but an advanced hobbyist could pull it off no sweat.
 

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Discussion Starter · #12 ·
Hi!
Sim Card soket in PDF attachment.
I bought a Chevrolet Bolt 2017 last year at a Manheim auction.
Onstar does not work for us. Different bands of cellular communications in Ukraine and USA.
Therefore, I found the telematics unit number that is put in the European Opel Ampera-E and bought it from OPEL INSIGNIA B II which has the same number.
 

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Wow, thanks for the link. Those sockets are hard to find (in the US anyways) but not impossible. They're not a common pad pattern at the usual vendors Digikey, Mouser, Newark, etc. Some weird distributor in Florida had 17 of them in stock (10 now) and we'll see what happens. The mini-sim form factor isn't so popular these days I guess.

I got mine at 115A-ADA0-R02 | ATTEND | NAC Semi - We'll see if they steal my credit card details or not...

AT ANY RATE, I'll see about doing this swap in the next few weeks with a Google Fi data sim card, and we'll see what happens. It's not as if Onstar's service is reliable enough to really miss. I keep track of the system status with a check every 30 minutes in Homeassistant, and the reliability leaves a bit to be desired. See chart for the last 3 days.

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Stay tuned.
 

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How are you determining OnStar status with Homeassistant? Are you using the token proxy service of https://github.com/q39JzrRa/GM-Vehicle-API to access the OnStar cloud services?

Do the OnStar cloud services work when replacing the eSIM with an alternative SIM? Otherwise it seems like there wouldn't be much benefit to doing this vs. just using a separate hotspot device, other than ability to use the roof antenna.
 

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Homeassistant is using the MyChevy integration that scrapes the website every 30 minutes. Not using the GM-Vehicle API, but I considered trying. The extraction key got deleted from the latest releases, which is a huge problem because now nobody can work on this without GM's super secret key. What a shame this project is dead, so sad. very discouraging. I don't even want to talk about it, nor do I think anybody else should talk about it.

Also, yeah... about the benefits... The roof antenna is probably better, and I don't have to use my phone or a hotspot device. Plus I don't own one.

I have my SIM sockets, my google Fi sim, a nano-to-mini adapter, and a crappy hot air rework station, and nothing but time on my hands, so I'm gonna give it a whirl.

I'll document.
 

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Oh boy.... so I did this modification today. Soldering sucked because I had an old iron who's tip wouldn't tin, and I had to remove two more interior panels than the PDF suggested. Then the ATTEND SIM socket had the right pinning but the wrong mounting pad layout, and the mounting tab happened to fall on top of some other contact nearby, so I had to file the tab off the socket and use a dot of CA glue to keep the sucker from only being held on by the electrical contacts.

Now, more importantly, there's something wrong and it doesn't work out of the gate. That's the first thing. I think YAM might be able to help me out with this one...

The head unit says it has 4G LTE connectivity, but the hotspot will not connect to my phone, or anything for that matter. I don't know what that's all about. It won't connect to Onstar either but that's no love loss. I'm using a tested working Google FI data SIM.

YAM, how did you configure your initial wifi settings?

Thoughts?

Thanks,
 

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Discussion Starter · #17 ·
In the WIFI settings, I looked at the password and simply entered it into the phone when connected to the Bolt access point.
And these are all my settings :)
 

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In the WIFI settings, I looked at the password and simply entered it into the phone when connected to the Bolt access point.
And these are all my settings :)
IT WORKS NOW - but here's the tiger trap...

You MUST have the hotspot enabled BEFORE doing this switch. This means you have to use the MyChevrolet app, or at least have the hotspot truly "enabled" before doing this mod. It's not the same as having it activated, but it does need to be "on" and as far as I can tell, there's no way to do that aside from using the app, unless of course it was already on. And yes, those settings can be found under wifi settings. However, even if the hotspot isn't active, it still broadcasts the SSID, but it won't allow clients to authenticate, except of course, the head unit.

I had to rip the head unit out AGAIN, switch back to the internal SIM, re-enable the hotspot with the MyChevrolet app, then switch back to the external SIM card, and then, voila, like magic, it worked. I was shocked. I was really hoping that I could adjust the wifi settings and whatnot with Keypass, but since it's super janky, I had no luck even connecting. It worked ONCE. I was going to try an iPhone, but I didn't have one handy. Onstar and telemetry is still busted even when you connect the head unit to your home wifi. Onstar probably looks up your car's subscriber info by the IMEI or something else on the internal sim, which obviously doesn't work anymore. Which is why I was hoping Keypass would work, as it's isolated bluetooth..

BUT IT WORKS, in the particular moment, it worked slowly.

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Ugh...
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Double annoying: - Hi airbag!
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Trim..
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Out comes the head unit...
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Hey there, ugly :cool: Don't disconnect anything but the blue USB.
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And then..
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And this is the insanely small thing you're going to solder... in my case, three times.
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I'm old and blind and I'm not going to screw around. Hence the microscope.
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(OK, gonna take a page out of YAM's book and make a PDF here, but moving on anyways, since I can't guarantee I'll get a chance)
THE SIM SOCKET - Right pinning, wrong mounting pad layout. You can see the mounting tabs are a bit ahead of where the exposed pads are on the board. I suppose on the right side I could have scraped away some of the solder mask and tacked it down, but on the other side, there was an active pad right there, or at least one that wasn't on the ground net, so that's a non-starter. I had to file it off. There are also two board locating posts on the bottom of the Attend socket that don't line up with anything on the PCB, so those had to get nipped off too. The takeaway? The Attend socket isn't the right socket. I tacked it with CA glue after soldering.
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Yeah not so much. I had planned to solder it though, as you can see I buffed the pads with some 600 grit! Probably a good idea on a board that's been sitting around since 2016.
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And here's the most important thing for would-be modders:
JUST POP THE TRIM OFF AROUND THE RADIO!!
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There's a panel UNDER the power button, gently pop that out FIRST, then carefully pop the trim out until you can access the head unit. It will save you a ton of trouble, time, and risk. As most people know, getting the panels on any plastic car to snap back to the way that they were and look right takes luck and, if you're fortunate to have any, experience. Suffice to say, there are no a-pillar trim removal videos on Youtube for the Bolt. Pulling the trim off the a-pillar sucks and should be avoided.

The speed varied from place to place, one time I was getting 6 mbit in the driveway, and down the street, almost 30 mbit, so it's all over the place. BUT if it gets a signal in places where the tiny chip antenna of a phone can't then it's all been worth it. The kids did do a ZOOM meeting with it in the TARGET parking lot, and it was as snappy and clear as at home, so I think overall it will be a good thing.

I'll get to work on that PDF, or,YAM, if you want to supplement your PDF with some more imagery, PM me and I'll share the whole album with you.
 

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Onstar and telemetry is still busted even when you connect the head unit to your home wifi. Onstar probably looks up your car's subscriber info by the IMEI or something else on the internal sim, which obviously doesn't work anymore. Which is why I was hoping Keypass would work, as it's isolated bluetooth..
Which has me wondering - what's the use case for this modification, other than gaining access to the rooftop antenna? Why not put the SIM into a phone and use that as the hotspot, if the telematics system still can't connect to OnStar services?

OnStar's insistence on always connecting through 4G even if wifi is available is utter garbage. It means that it's horribly unreliable in my garage thanks to the fact that I have strong wifi but very weak cellular signal down there.

Since you've been mucking around behind the dash panels - what would you say is the easiest place to get access to the "dirty"/"isolated" CAN buses (the ones on the infotainment/telematics side of the SDGM)? I'm looking into using a Macchina P1 to replace most if not all of the OnStar functionality, and in addition to preventing the telematics device from doing certain things to the vehicle, the SDGM also filters out any messages that originate on the main buses but should be originating on the "dirty" bus, so you can't issue an unlock or precondition message from the OBD connector. (You can trigger a wakeup, but you can't actually do much useful once you've woken up the buses.)
 
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