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An old post here mentions there are 5 data bus systems.
Yeah, I know. I'm trying to get at ones that are NOT wired out to the OBD connector and/or are firewalled from it. To my knowledge, for the low speed SWCAN bus, there's only the "clean" and "dirty" buses on either side of the serial gateway module. There are also multiple high speed CAN buses, and at least one that is of interest is NOT accessible from the main OBD connector. GM historically has wired at least one additional CANbus to pins 3+11 of the OBD connector, but they are unpopulated on a 2020 Bolt.

Which means I need to find other places to access them. Unfortunately the only documented access point I've seen is the camera connector on a vehicle with DCII - that has the Object Detection bus and the SWCAN bus.

The secondary passenger-side diagnostic port is not present on a 2020 as far as I can tell. I've looked all over the passenger footwell area and no evidence of a second diagnostic connector.

Edit: A lot of twisting and contorting and the BCM is right behind the OBD connector, it's a possible splice/breakout point if I can find out who manufactured those connectors. Unfortunately the BCM connectors are probably a rarer connector even by automotive standards...
 

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The secondary passenger-side diagnostic port is not present on a 2020 as far as I can tell.
Lol. That's why I knew about the other thread. I came across the passenger side port the other day on my 2017. It's pretty obvious and all the way to the right side. So I started googling the forum about it. I was actually looking where the pedestrian module is. Rumor is, it's in the center console. I bought a spare module and thinking I might need some can bus tools to talk to it. And maybe sniff out its connector on the car.
 

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Have you guys looked in the Service Manual?
According to what I’m reading in the Service manual, the “Frontview Camera - Windshield” is connected to both the “High Speed GMLAN” and the “Low Speed GMLAN” and in the center dash is the telematics communication interface control module is connected to both the “High Speed GMLAN” and the “Low Speed GMLAN” via the X84 Data Link Connector.

The X84 Data Link Connector (DLC) is a standardized 16-cavity connector. Connector design and location is dictated by an industry wide standard, and is required to provide the following:
Terminal 1: Low speed GMLAN communications terminal
Terminal 2: Class 2 communications terminal
Terminal 3: Object high speed GMLAN serial bus (+) terminal
Terminal 4: Scan tool power ground terminal
Terminal 5: Common signal ground terminal
Terminal 6: High speed GMLAN serial data bus (+) terminal
Terminal 7: Keyword communications terminal
Terminal 11: Object high speed GMLAN serial bus (-) terminal
Terminal 12: Chassis high speed GMLAN serial bus (+) terminal
Terminal 13: Chassis high speed GMLAN serial bus (-) terminal
Terminal 14: High speed GMLAN serial data bus (-) terminal
Terminal 16: Scan tool power, battery positive voltage terminal


The X84B Auxiliary Data Connector is a standardized 16-cavity connector. The pinouts for this X84B Auxiliary Data Connector are as follows:
Terminal 3: High Voltage Energy Management high speed GMLAN serial bus (+) terminal
Terminal 4: Scan tool power ground terminal
Terminal 5: Common signal ground terminal
Terminal 8: Ground terminal for Auxiliary Data Connector identification
Terminal 11: High Voltage Energy Management high speed GMLAN serial bus (-) terminal
Terminal 12: Powertrain high speed GMLAN serial bus (+) terminal
Terminal 13: Powertrain high speed GMLAN serial bus (-) terminal
Terminal 16: Scan tool power, battery positive voltage terminal

But, it's a very unwieldy PDF. (Bought a copy from eBay)
 

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No, I haven't looked at the service manual because I'm not paying $400 for a manual that isn't for my model year, and they aren't selling 2020 service manuals anywhere yet, other than possibly the $20/3 days TDS subscription which I MIGHT go for if nothing else. I was hoping that someone who does have a service manual could find some useful info, and you have.

The passenger side port must be missing on 2020s or relocated, because if it exists, it sure isn't obvious any more. :( Just to be clear, all the way to the right side of the passenger footwell, or by "passenger side" are people meaning "passenger side of the drivers' footwell"? (I haven't seen anything obvious there either, but with a bit more info I can look harder.)

Terminal 1 (low speed GMLAN) and 6+14 I already knew - 6+14 is the main CANbus that all basic OBD adapters talk to.
3+11 being object and my vehicle not having DCII are consistent - mine does not have anything populated on 3+11. Even if I did have DCII, these are supposedly on the wrong side of the Serial Data Gateway. Even if they weren't, you'd have to disconnect the camera in order to keep it from fighting OpenPilot.
12+13 for chassis bus is news to me

X84B pins 3+11 is the high voltage bus, that's actually the bus I really wanted to sniff to get high-resolution battery data from. Powertrain bus is also likely to have useful stuff to passively monitor. If only I could FIND X84B...

What you're describing implies the telematics (onstar) module is on the same physical bus as the OBD connector, but all documentation I've seen along with my personal experience is that there's a serial data gateway as a firewall in between. Unless maybe this was added sometime in the 2019-2020 range and isn't present on 2017 models?
 

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No, I haven't looked at the service manual because I'm not paying $400 for a manual that isn't for my model year, and they aren't selling 2020 service manuals anywhere yet, other than possibly the $20/3 days TDS subscription which I MIGHT go for if nothing else. I was hoping that someone who does have a service manual could find some useful info, and you have.
Well, for a few bucks you can have your own?
 

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Yup, definitely missing on my 2020. The mounting hole for it is not, but the connector is. Is there a smaller connector that is going into that black thing that's at the base of the glovebox right where the hinge is?

Thanks anyway!
 

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Yup. OK, so definitely not a "replacement" for that connector. Also you had a much better viewing angle, it's clear that it only has two wires. I could've sworn I saw more.

Probably some sort of "glovebox open" signal - maybe for the airbag systems? Is that the passenger airbag module?

I'm surprised Chevy doesn't have SOME access to those buses for diagnostic purposes, so where is the connector on 2020s?
 

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LOL. Yeah, I'm not messing with that either. I wish I could find where they relocated that diagnostic connector to... It has to be somewhere???
 

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$25. Just ordered one myself. If it's for real there probably more info there than I'll ever use. If it's a rip-off, well then it's only 25 bucks.
 

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As far as being a real service manual - it appears to be.

As far as being legit - being on a CD-R with a volume ID of "New" says to me it's probably pirated... But since Chevrolet won't even sell the service manual for my model year (2020), I really have a difficult time feeling guilty about this as a private end customer. GM treats private end customers like crap, both in terms of service documentation access and vehicle API access - there are apparently some really sweet APIs available to access OnStar functionality if you're a commercial fleet partner. The rest of us have to live with the MyChevrolet mobile app and nothing else.

One other observation: While the manual does have an index on the side, the original manual appears to have cross-references, while the cross-references are not clickable in this one. Minor annoyance given how much money was saved.
 

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So an aftermarket self-driving kit? Yeah, no thanks. I'm willing to take risks in my life, but that's not one of them, especially when doing so could very well kill somebody else too.
 
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