Trouble code U0100 - GMC Acadia Forum: AcadiaForum.net
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post #1 of 11 (permalink) Old 02-27-2019, 07:20 PM Thread Starter
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Trouble code U0100

While driving my 2010 Acadia SL one night the doors unlocked and locks about three time and motor seemed to stumble just a little. Turned around to head home and drove fine no problems for about 20 minutes. Next morning went to start and it ran for about a second then died. Tried to restart and engine cranked for about half a second then stopped. Now it does not turn over at all and no noise from engine bay. Rear hatch also won't open with remote, button on dash or button on hatch itself. Engine light is not on but there is a code U0100 ECM or PCM not communicating.
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post #2 of 11 (permalink) Old 02-27-2019, 07:30 PM
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Here's some information for your reading 'enjoyment:' https://www.obd-codes.com/u0100 The ECM and PCM are in one combined module easily accessible under the hood. The TCM is inside the transmission.

2007 Acadia SLT-2, 'HiYo' Silver outside, Ebony/Titanium inside, no NAV, no HUD, no errors

Last edited by speleos; 02-27-2019 at 07:35 PM.
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post #3 of 11 (permalink) Old 03-01-2019, 12:49 AM
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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!
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post #4 of 11 (permalink) Old 03-01-2019, 08:51 AM
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We are seriously screwed when a faulty driver's door window switch can create enough electronic feedback to cause an engine running problem!!


2007 Acadia SLT-2, 'HiYo' Silver outside, Ebony/Titanium inside, no NAV, no HUD, no errors

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post #5 of 11 (permalink) Old 03-01-2019, 09:23 AM
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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.
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post #6 of 11 (permalink) Old 03-01-2019, 10:12 AM
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@Tmcg, what's your background? Are you a tech, instructor, or engineer?

2007 Acadia SLT-2, 'HiYo' Silver outside, Ebony/Titanium inside, no NAV, no HUD, no errors
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post #7 of 11 (permalink) Old 03-01-2019, 11:02 AM
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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!
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post #8 of 11 (permalink) Old 03-01-2019, 11:17 AM
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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.
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post #9 of 11 (permalink) Old 03-01-2019, 11:31 AM
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Quote:
Originally Posted by Tmcg View Post
... 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. ...
Let's hope industry sees this before they unleash autonomous vehicles on us.

2007 Acadia SLT-2, 'HiYo' Silver outside, Ebony/Titanium inside, no NAV, no HUD, no errors
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post #10 of 11 (permalink) Old 03-01-2019, 11:34 AM
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Quote:
Originally Posted by Tmcg View Post
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.
That's OK. I deleted my comment before I saw your response to it. I undeleted it to keep confusion to a minimum.

2007 Acadia SLT-2, 'HiYo' Silver outside, Ebony/Titanium inside, no NAV, no HUD, no errors

Last edited by speleos; 03-01-2019 at 11:41 AM.
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