[Tmcg]

Greetings, I had similar problems.
2016 Acadia Denali. I bought a GM MDI interface and a GDS2 software lease from GM so I could troubleshoot mine. I had many strange electrical problems, culminating with the car not starting. The very first subtle thing I noticed was that the auto up on my driver's window switch stopped working. Then very slow responses to door lock commands and weird things like running lights in one headlight randomly not working. Upon initial diagnosis, I found that almost half of my modules had various communication DTCs set. The other half of the modules simply wouldn't respond when requesting their fault codes. So, after unplugging some modules, rebooting the car by disconnecting the battery, I got all my modules to respond. All of them had communication DTCs set which in themselves do not indicate a problem with that module. One of them had a serious hardware DTC set. It was the first one that misbehaved, the driver door switch module, with an internal checksum error. This code basically means that the module has declared itself insane. So, I experimented by simply unplugging my entire driver's door by pulling the connector at the front door pillar. Wouldn't you know my Acadia sprung back to life, starting and behaving normally with the exception of the drivers door being dead, the radio complaining that its front left speaker was gone and the airbag computer couldn't see the impact sensor in the driver's door. This also confirmed my early suspicion that one insane module was screaming on the bus, annoying all the other modules. Strangely though, after resetting the door switch module several times, and reteaching it where the auto up limit was, my Acadia has been working great for over a week now. I dont trust this module though, so I ordered a new one from Rock Auto for $133. It is supposed to be preprogrammed and it has a 3 year warranty. Made by "Standard" with original Bosch label and part number on it. I will be putting it in tomorrow. I'll update you with my progress ASAP. God bless!

 

[Tmcg]

Absolutely. But unfortunately that is exactly the case. If you grounded the communication lines you would have the same issue. Newer cars are too dependent on these individual modules being able to communicate with each other to operate the car. This could easily be improved though if modules were more fault tolerant. Speaking as a designer of critical communication equipment, modules should be designed to be more immune to "bus noise". Each module should also be equipped with "watch dog circuitry" that could lock it out in the event of hardware faults like an internal checksum error. The cost of doing this is practically free in most cases too. It's more a mindset as a software and hardware engineer verses many hours of extra coding and more parts inside the module. Now, that being said, simply getting the DTCs out of all the modules is very useful. I had to spend too much money to get to that point. My OBDMX has all the hardware equipped to communicate with all the modules. If the PIDs were published, i could have effectively diagnosed this issue with it. All I could see was the communication DTC logged by the ECM.

 

[Tmcg]

Hardware, software, component and test engineer. I've progressed through each of those during my career. In my current position I get to wear all those hats at once, LOL!

 

[Tmcg]

Sorry Speleos, my last post was a reply to your post or question and my post went here and now I dont see your question. My apologies if that did not work correctly. Please fix my post or let me know how I should fix it.

 

[Tmcg]

All went well installing the new driver's door switch module. There are some good videos on YouTube that I followed to remove the door panel. Just take your time and you won't break any plastic clips. There is no guarantee that your communication DTCs are a result of your driver door module. Get access to a diagnostic tool that can obtain codes from ALL modules and look for the module(s) with serious hardware DTCs not just communication DTCs. If a module is not suspected, there could be an intermittent communication line short to ground somewhere, which can cause communication DTCs. One major note though, in my 2016, even though the new module was indeed preprogrammed and my MDI showed nothing wrong with it, it only operated my driver's door window and lock. It was sending out messages for all of its buttons as reported by the MDI, but the other modules were ignoring it because the VIN was not programmed into it, "VIN learned: NO". The passenger door switch module parameter for VIN learned was "YES". After programming the module, all the other modules were happy to listen to it and all buttons and lights operated correctly. Then I noticed my window lockout switch even worked. That never worked since I bought the car, I just forgot about that.
I believe earlier Acadia models are less finicky and these "pre programmed" modules will drop in without reprogramming, but depending on your year, you may have to visit a dealer or friend with an MDI for programming after installation. ($40 subscription per car) For now, all modules are happy with each other and I dont see any more communication DTCs. Enjoying my Acadia again.
God Bless.