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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.

---

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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Discussion Starter · #11 ·
I had a dealer replace the TCM. It cost around $1100 total.

Unfortunately, about 2 months afterwards, we had intermittent issues (similar but different) on cold starts. Ended up back at the dealer for a month trying to diagnose. Eventually they guessed that the other issue was the Park Neutral Switch/Sensor. That repair cost about another $800, most of which was diagnosis and labor. Wish they'd have done it at the same time and saved myself $500+ ??‍♂

Now that those are both fixed, we haven't had any more problems. However, my wife and I both feel that the Acadia doesn't shift as smoothly anymore. Not sure if it's a true difference or we're being more attentive, but we're not happy with it.
 

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My wife’s 2014 Acadia recently had the P1682. After some research I found a tech bulletin about this issue: Bulletin No. 19-NA-276

I dug into it and I believe the problem is solved. It was the fuse block connection under the hood. The connection between the prongs of the upper section that mates with the terminal block female connection of terminal 51. Terminal 51 in X50A fuse block -underhood X3. The male prong/stab had a burnt spot/ electrical arc spot visible on it which meant there was not a tight fit in the male to female connection. I was able to increase the tension of the female connection by means of bending the female connection slightly. I also cleaned off the prong/stab of the male connection and reassembled the fuse block.

It’s been 2 weeks so far and the problem has not yet returned. It was happening on a daily to every other day. Included in the tech bulletin is the instructions for the repair by replacing the terminated lead of terminal 51 with a new terminated lead. I didn’t replace it but I did order the part and if it happens again I will replace it. Here are some of the pictures I took of it.

Best Reguards,
Randall

Bumper Automotive exterior Metal
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My wife’s 2014 Acadia recently had the P1682. After some research I found a tech bulletin about this issue: Bulletin No. 19-NA-276

I dug into it and I believe the problem is solved. It was the fuse block connection under the hood. The connection between the prongs of the upper section that mates with the terminal block female connection of terminal 51. Terminal 51 in X50A fuse block -underhood X3. The male prong/stab had a burnt spot/ electrical arc spot visible on it which meant there was not a tight fit in the male to female connection. I was able to increase the tension of the female connection by means of bending the female connection slightly. I also cleaned off the prong/stab of the male connection and reassembled the fuse block.

It’s been 2 weeks so far and the problem has not yet returned. It was happening on a daily to every other day. Included in the tech bulletin is the instructions for the repair by replacing the terminated lead of terminal 51 with a new terminated lead. I didn’t replace it but I did order the part and if it happens again I will replace it. Here are some of the pictures I took of it.

Best Reguards,
Randall

View attachment 10351 View attachment 10352 View attachment 10353 View attachment 10354
Found the same TSB and an earlier one form 2018 GMC TSB PIT5643 . Found your response and a few others as well with the P1682 issue I've been having on my 2014 Acadia SLT. Notice quite a few fuses ( PCM ignition and ECM in particular) had blackened prongs/contacts on them, but not blown. I'm thinking that's indication of getting too hot. I went ahead and ordered the fuse box itself, it'll take 6-10 days and hopefully issue solved. We are lucky my wife works from home currently ( thank you covid?) so we really only use the Acadia for a few miles each day to drop the kids at daycare and then errand running on the weekends ( car is rarely ever running for longer than 30-45 minutes straight). Sometimes we go a week without issues, other times it'll happen a couple times in a single day. Very random.
 

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My wife’s 2014 Acadia recently had the P1682. After some research I found a tech bulletin about this issue: Bulletin No. 19-NA-276

I dug into it and I believe the problem is solved. It was the fuse block connection under the hood. The connection between the prongs of the upper section that mates with the terminal block female connection of terminal 51. Terminal 51 in X50A fuse block -underhood X3. The male prong/stab had a burnt spot/ electrical arc spot visible on it which meant there was not a tight fit in the male to female connection. I was able to increase the tension of the female connection by means of bending the female connection slightly. I also cleaned off the prong/stab of the male connection and reassembled the fuse block.

It’s been 2 weeks so far and the problem has not yet returned. It was happening on a daily to every other day. Included in the tech bulletin is the instructions for the repair by replacing the terminated lead of terminal 51 with a new terminated lead. I didn’t replace it but I did order the part and if it happens again I will replace it. Here are some of the pictures I took of it.

Best Reguards,
Randall

View attachment 10351 View attachment 10352 View attachment 10353 View attachment 10354
Update as of today Jan 16th 2021

Well the car ran flawless until it threw the same code again today while my wife was bringing me some food to my place of work. She stopped and cleared the code with my scan tool. And away she went. So I’ll have to revisit the fuse block and take another look at the terminal to see what, if any, signs of arcing it may show.
 

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Update as of today Jan 16th 2021

Well the car ran flawless until it threw the same code again today while my wife was bringing me some food to my place of work. She stopped and cleared the code with my scan tool. And away she went. So I’ll have to revisit the fuse block and take another look at the terminal to see what, if any, signs of arcing it may show.
Any update Randalledelphia?

My wife just had this occur again. Called dealer as I'm not brave enough to do the service bulletin work that will be needed. They will look at it next Wednesday morning. Curious to see what they tell me though I'll take the fuse block off and look at the terminal contact. If it's got a black area again I know it (the terminal below-X50A) is the issue since the fuse block is brand new. cheers Will update once done with dealer next week.
 

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Any update Randalledelphia?

My wife just had this occur again. Called dealer as I'm not brave enough to do the service bulletin work that will be needed. They will look at it next Wednesday morning. Curious to see what they tell me though I'll take the fuse block off and look at the terminal contact. If it's got a black area again I know it (the terminal below-X50A) is the issue since the fuse block is brand new. cheers Will update once done with dealer next week.
Update as of 5-6-2021
Since the last occurrence in January, I checked the terminal again and indeed the terminal was loose and arcing. I made the repair to the terminal and insured a tight connection between the male and female terminal connections. After this repair in January, I have not had any more problems with the car throwing the codes anymore.
I hope this helps.
 

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Update as of 5-6-2021
Since the last occurrence in January, I checked the terminal again and indeed the terminal was loose and arcing. I made the repair to the terminal and insured a tight connection between the male and female terminal connections. After this repair in January, I have not had any more problems with the car throwing the codes anymore.
I hope this helps.
Was it a difficult repair? I feel like it involves replacing wires.
 

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Was it a difficult repair? I feel like it involves replacing wires.
It was not difficult for me. You can splice in a new pigtail with the female connector on it. I however, modified the existing female connector to make it fit tighter on the male. I basically just crimped the sides in a bit more. IF I have any more issues I will splice a new section of wire with the new female terminal on it. I have a new one ready to go.
 

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It was not difficult for me. You can splice in a new pigtail with the female connector on it. I however, modified the existing female connector to make it fit tighter on the male. I basically just crimped the sides in a bit more. IF I have any more issues I will splice a new section of wire with the new female terminal on it. I have a new one ready to go.
I'll check this out tomorrow morning. Did you remove the female terminal from the box or just use something slender to slide down in and press down to make it tighter?
 
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