Andybump

Ok, so from the above description, the passenger side antenna is the "primary" one. It seems disconnecting that one is causing enough of an error in the system to stop onstar from transmitting data, as we saw from my experiment with the tire. I think so. I was hoping to find something in the manual that said it shut down the 4G commes but did not. The left and right antenna connections to the telematics module do both show two way.

There's nothing else inside the passenger side antenna box - just the primary cellular - so nothing else should in theory be affected. According to diagnostics, several satellites are connected to GPS, so that appears to be working fine. Good. I was concerned that it might shut down everything, not just cell comms.

The way the diagrams are drawn (with arrows in both directions) and the above wording from the service manual, I believe the passenger side antenna, being "primary cellular", is for doing two-way communications. It shows two way comms to the telematics module. See attached.

Diagram for secondary implies receiving duties. Which would make sense since "diversity antenna" setups use a pair of antennas to improve *reception*. You would not transmit from a pair of antennas unless you're using interference to target something at a specific location. Interesting point. I might have designed it to transmit via the antenna that also received the strongest signal. But I do not know what they did, and can find no evidence of how the secondary path is used.

The car has lost its ability to transmit tire pressure info since I disconnected the Primary Cellular antenna, and the feature was restored within a minute of reconnecting that antenna. Only the primary appears to be capable of being used for transmitting. So I'm satisfied that OnStar can not receive data from me via cellular. I think so. I'm still interested in what happens when back together and you drive around a bit.

The car does not have access to any password protected Wifi network. Whether the car would use an open wifi network to upload stored data is unclear, but I believe this is very unlikely given the security issues of connecting ***** nilly to an open network. So I'm comfortable with that until I get it near open wifi to make sure it doesn't connect and use that wifi. Again, seems quite unlikely to just start using wifi without at least asking me. Do we know if it would even send telematics by wifi? I could repeat my tire experiment with a wifi connection active. Yes, I think it would send the alert via WiFi if connected. I wonder if it will also notify OnStar about the perceived issue with the antenna and send a diagnostic about that. I agree that it very likely will not connect to any networks unless you ask it to do so via the menu in the car.

I'm feeling pretty confident this problem is solved. I think so. I think there is a very very small chance that the secondary path might somehow wake up and transmit something. I just wish I could find more info about it.

Andybump

One point on interpreting the schematics and the text. The schematics appear to include various different configurations in the same illustration. So for example, UQT is the code for the Performance Data Recorder (PDR). This schematic is showing the path if you have the option (UQT) and if you do not have the option (-UQT). The very inconspicuous - signt in front of the UQT. So if you have PDR, the signal splits, with cell and GPS signals to the Telematics, and GPS signal to the PDR.

The text is similar. There are configurations without Nav (IOT upgraded, IOS standard infotainment system) and I think neither. And configurations without OnStar (UE1).

There are very long descriptions of the operation, and the specific configuration is only mentioned at the start of the paragraph. So, you can be reading along and then discover non of it applies. The diganostics sometimes indicate the applicable configuration at the top, but sometimes have the differences buried in the procedure.

When I post info from the manual, I try to select the applicable configuration for the US market with OnStar.

22c8z51

For scientific / educational purposes, and just to sum everything up so far in one place. Let us know your observations! I won't have time for more testing for a while.

Dan Hintz

Diversity systems work by looking at the receive power for all antennas involved and selecting the one that has the highest signal power... obviously all antennas are receiving at the same time, but the diversity system only passes along the signal for a single antenna to the receiver.

Transmitting from more than one antenna at a time (on purpose) would be for beam steering... I can guarantee there is no beam forming in the OnStar system.

meesterover

Thank you! Now to figure out where this is located on the Sierra and XT6.

D0lphan72

Thank you for looking into this as I have big concerns. When I buy my C8 I may or may not be taking advantage of that big V8 & don't want my driving habits provided to insurance.

Couple of questions about disconnecting the antenna. Will Apple carplay/ radio/ Bluetooth for music & phone be affected? I see you lost tire notifications but can you still see the tire pressure & heat? Anything else of note that might be affected?

123sugey

Received my LexisNexis report in the mail yesterday. 150 pages … 150 pages !! Much more in depth than a background check !!

Andybump

I have been reluctant to go to that site. How much information about yourself must you supply to them in order for them to release the report to you?

Is it like credit reporting agencies, you can get your info, if you share things like you SS, birthday etc. I'm not excited about going to a strange web site and supply data to them in order to get what they might have already. I could make matters worse.

D0lphan72

Hi, you seem to have been engaged in figuring out the removal of the antenna. Not sure if you're able to answer my questions a few posts above but could you take a look & let me know if you know the answer to any of them?

Andybump

He disconnected one cell antenna and it appears to shut down the cellular comms only based on what he said. GPS still works, thats connection to the left side, multifunction antenna. Neither of those antennas has anything to do with BT or WiFi. BothWiFi and BT connections are provided by the "radio", not telematics. So, you should be able to use the phone with BT, or wireless car play which requires both BT and Wifi. You can always also use the direct cable connection fo support CarPlay.

The only tire notication lost was the one sent via the cellular notification. This will not affect on board tire pressure monitoring and alerts.

If the goal is to shut down the data sharing, however, I think there may (repeat may) be an issue since WiFi still works. If the WiFi connects to an external internet enabled network, such as your local WiFi in your garage, it might (repeat might) send the same data to OnStar that it would have via the cell connection. We know that the WiFi connection will support receiving of OTAs, will support download of apps, and while connected it will proved data needed to support those apps. For example if you have a pandora app in the infotainment system, but no data plan (or no cell connection) , but you connect to the external network in your garage, it will receive the necessary data and play music. I think that the WiFi cannot connect to a network without being requested to do so via the car menu - if I am right - then one could prevent that connection. The phone can also connect to the car "hotspot" as a connected device - and that is how it connects when it supports wireless carplay (at least prior to 2024). I can see all this on my 2021 menus. However, when its connected to support wireless carplay, I think (guessing again) that does not see that as an internet connected network (even though the phone is connected to the internet) and so it will probably not try to send data to OnStar when connected that way. Lotta "if I am right" s in this missive.

D0lphan72

Appreciate the write up. Sucks to see that no matter what I do the insurance companies are going to know my driving habits in my car & will be able to charge more if I were to drive aggresively

rawbar

I will know within 30 days if I was successful in getting these records purged from LN. If I was, I will share the process I used. I am not covered by CCPA or any other state's privacy laws, so if this works, it should work for anyone. Fingers crossed

theseal

great thread, much appreciated.

the only way any responsible american would ever own any car is with all of the car's ability to send or receive any data or commands to or from anyone, anywhere, any time, completely, permanently and totally disabled.

Anything else means you dont actually own the vehicle, and are nothing more than a potential victim of all kinds of misconduct.

Since all the car manufacturers and governments are making responsible american ownership extremely difficult, i really appreciate the info on this thread.

While my c8 z is mechanically interesting in some respects, and does a lot of pretty impressive things for a factory car, it is also just a disposable short term asset due to these defects. Once my real car is finished, I'll be selling it. or if i just fall in love with it, the only way i would own it is to rewire the entire car properly and throw all that **** out.

The solutions being discussed here are a very welcome middle ground.

Dan Hintz

This isn't a difficult thing to check for, but from the sound of 24's schedule (and possibly his limited computer skills), he may not be the person to do this work. In a nutshell, one would need to simply look at whatever connections are being made through the WiFi router... I don't think something as detailed as a WireShark log is required here (though it may be useful for a long-term dig into what info is being sent to OnStar), just a look at what servers the car is connecting to. If it connects to an OnStar server, there's your answer.

Andybump

I was thinking of the same test done for the 4G connection. With the 4G not connected, and the WiFi not connected - let air our of the tire. See if a notice is received. I expect not as that was the first part of the test he already performed. Now connect it to the local WiFi in the garage. I'm betting the notice appears immediately, indicating it send out data to OnStar via that path.

Similar test, only now use the phone in hotspot mode and connect it as a network. Again, I'm betting the message appears right away. I think you have to start each test, with correct inflation and let air out, it may trigger on a change.

Finally, once more, only now connect the phone to support car play. I'm betting it does not transmit the alert.

SuprChrgdC7

cant we just wrap the antennas in a faraday bag? no signal sent to the outside & nothing turned off. i use my cell for GPS.

rawbar

Already covered above in this thread Didnt work.

gatorfl

I wouldn't think the car would have some built in storage setup that would allow the info to build up until its connected again. I assume its like a phone and just connects to the nearest towers and transmits live and the receiving unit/ software analyzes and group it for the month or so on.

I also doubt GM would have made it to transmit that data though any other method. So far this looks like an easy (reversible) way to stop it.

Dan Hintz

Just make sure the TPMS sensor is transmitting. They go into a low-power sleep mode after a certain time period of just sitting (i.e., not spinning), and I'm not sure if they wake up just with a change of pressure (but probably not). It would suck to go through all of that testing only to realize the tests were faulty because the sensors weren't transmitting in the first place ;-)

Dan Hintz

Cell is the transmission medium... anything else would require a nationwide (worldwide) infrastructure that just doesn't exist. Small memory chunks (e.g., RAM) are pretty cheap (and often readily available on whatever processor is being used), so it would be dirt simple to have a small data buffer... if there's no cell service, collect the data until such time as service returns. If data is lost because you've filled the buffer before service is restored, it's not the end of the world. Plus, it's more efficient to transmit bursts of info rather than single bits/events every time they happen, so a buffer is actually the more likely solution (and you get the added benefit of being able to prioritize events for retention... e.g., a low tire pressure is more important than a hard-baking event).