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Discussion Starter #1
I have a 2013 Acadia with ~108k miles on it, which I've owned for a little over a year.

A few days ago, I had several issues all pop up at the same time (listed below). As suggested in a couple of similar threads, I replaced the Brake Pedal Position Sensor and cleaned out the Throttle Body. Those changes appear to have resolved the first two issues and now I have two different codes (U0101, P1682).

Most of these issues started within a mile of leaving my house and while I was driving around 35-40 mph. The first thing I noticed was a very loud thunk, like I hit a large pothole, but I was on a smooth road. The same thing happened again and each time felt like a very rough shift or something. Then, the "Traction Control Off", "Stabilitrak Off", and service warnings came on, but no check engine light. I pulled over, shut the car off for a minute, turned it back on and let it idle for a minute and it seemed fine, although the warning messages were still on. I turned around to drive home and again got the same clunk after getting up to around 40 mph. Then, the door locks started making the on/off sound pretty continuously/erratically, but not actually unlocking the doors.

Issues
  • Rough shifts (?) at random intervals (resolved with new Brake Pedal Position Sensor?)
  • Door switches with a mind of their own (resolved with new Brake Pedal Position Sensor?)
  • Warning Messages
    • Traction Control Off
    • Stabilitrak Off
    • Parking Assist Off
    • Service Traction Control
    • Service Stabilitrak
    • Reduced Engine Power (only displayed occasionally and after the initial issues began)
  • Limited to 2nd gear (after I got back home and started it again later)
  • No gear selector indicated
  • No backup camera
  • Single beep sound when coming to a stop
    • Sounds like the beep you get when the parking sensors go off while backing up
  • Doors don't unlock automatically when put into park
  • Trunk won't open
Engine Codes

I had the engine codes read today at AutoZone, which were:
  • U0101: Lost Communication with Transmission Control Module (TCM)
  • P1682: Ignition 1 Switch Circuit 2
I had AutoZone reset the codes in case they were left over, but they came back on right away, with all remaining issues. I did some research on these codes, but they appear to be unrelated and somewhat difficult to diagnose (multiple possible causes).

Can anyone give feedback on what might be causing these and/or some ways I can troubleshoot this?
 

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Look at this information about P1682 from the Traverse forum. It should be helpful since Acadia and Traverse are essentially the same vehicle. 2014 p1682 Could be the 'U' code is related to it.
 

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Discussion Starter #3
I took a look at the ECM (I think?) which I've seen mentioned several places, mostly due to bad connection or fraying wires, etc.

On mine, I noticed that the top connection wasn't fully seated and the red switch was unlocked. I removed the top connection, reseated it and latched the lock. When I turned the car on, the check engine light was off, but all other symptoms persisted.

I've driven it a little more and turned it off a few times and the check engine light did just come on again, although I can't check the codes to verify they are the same.

8773
 

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Discussion Starter #4
I drove this to an independent mechanic to have the issue diagnosed and they confirmed that the Transmission Control Module needs to be replaced.

They said they can do the repair, but they have to purchase the TCM from the dealer, then have the car towed to the dealer for programming the TCM, so they suggested it might be better to just have the dealership do the repair. I called the dealer and was quoted ~$1,050 total (including tax).

I am considering following the instructions on this forum post to perform the repair myself, which will cost ~$400 in parts and ~$100 in tools that I don't have already. I will first try replacing the TECHM pressure switch laminate discs (membranes) as suggested by @speleos in the same thread. If that does not work, then I will have a replacement TEHCM on-hand to install.

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Dealer Pricing Breakdown

DescriptionPrice
Labor (3 Hours @ $95/hour)$285.00
Transmission Control Module$545.00
Seals/Gaskets/Etc.$116.00
Transmission Fluid$20.00
Total$966.00
Total with Taxes$1,043.28

DIY Pricing Breakdown

Rebuild Pressure Switch


Replace TEHCM

 

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@travisw, you'll likely find the TEHCM in your Acadia's transmission doesn't have the laminate disks. 2013 was the year GM changed the 6T75 TEHCM to a Gen 2 design using different technology.
 

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Discussion Starter #6
Well, that's unfortunate but I appreciate the forewarning. Does that mean I'm just looking at a straight up TECHM replacement? I'm assuming there's not any intermediate rebuild/repair that might be possible.
 

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Well, that's unfortunate but I appreciate the forewarning. Does that mean I'm just looking at a straight up TECHM replacement? I'm assuming there's not any intermediate rebuild/repair that might be possible.
I haven't read about any DIY rebuild for the Gen 2 TEHCM.
 

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I would let the dealer do it to get the 12 month/12k mile warranty on the repair.

If you do it yourself and you value your time at $0 an hour, you get what you pay for.
 

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Discussion Starter #9
@divotdug I'm weighing that option pretty heavily at this point. If the difference were $1,000+, then I'd probably DIY more readily. With only $4-500 difference, peace of mind is probably worth it alone, not to mention I won't have to spend my weekend cursing at the car while I try to fix it. 😅
 
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travisw
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