Have a 22 SR 3LT HTC with 15k miles, purchased new and has had all recommended service performed by dealer. Never tracked etc.
Early on, soon after taking delivery it threw a DCT related CEL (acted normal). Dealer performed a filter change/flush along with some sort of updates to the TCM. Since then, no issues whatsoever.

Until now…

Car threw a CEL on or about August 1 but continued to behave normally. On August 6th I took it to my area dealer and they pulled the codes in the service drive for me. DCT error codes (below) were reviled.

Was told I could leave it there but they’d not be able to get to look at it for a couple of days or just take it home and bring it back Thursday morning. I chose the later. On the way home from the dealer I stopped to get gas, upon restart the CEL disappeared. Called the dealer as decided not to bring it back in. Again, the car was seemingly acting normal.

On September 3, after just 200+ miles of “normal driving” the CEL reappeared, this time during a stop light ladened trip, in which the DCT would sporadically act abnormal. Sometimes seemingly holding a gear too long. Sometimes seemingly downshifting prematurely and other times acting perfectly fine.

Back to the dealer last Tuesday September 6th wherein the same DCT codes were pulled. 16 miles trip to dealer, car acted/performed fine. Left car and to date no work has been performed but GM tech is apparently/supposedly analyzing data. My service writer told me that “they’re very good at what they do, but not particularly fast”. I’m not at all feeling good about this. I feel that early on it would be a new tranny candidate, but now into year seven, they’re more inclined to attempt to diagnose and repair. Guess I’ll find out. Having heard/read stories of cars being out of service for 30-40 or more days concerns me. Especially since it will apparently sit idle outside in the Texas sun/heat (again 3LT).

Will see what Monday brings as a week will have gone by. This DCT issue is obviously real. I know many will say it’s only a small percentage of cars. Matters not if it’s you. The other thing that has to be considered is that while some C8’s are daily drivers, the vast majority are not. So while my car is nearing four years old, it’s yet to pass 16k miles. Typical one year of use for a daily driver. Covered by the powertrain warranty but past the window for a potential lemon law repurchase.

Anyone else have a service experience triggered by these codes? Curious as to the outcome and the length of time to remedy…

 

Hopefully the dealership will give you some positive news soon - hate to think of having to leave the car at the dealership for a long period of time or have to do major surgery on the car.

 

Fortunately, you are still covered by the power train warranty, that could end up being a very expensive fix

 

Did you have the dct filter changed at 7-8k miles and the fluid replaced at 3yr?

 

YES & YES
Filter was actually changed twice. Once at roughly 2200 miles and again at 7800.

 

Wiring/Harness Inspection → Especially for P1950 and P1967, connection faults are common.

Valve Body Solenoid Check → If stuck, the valve body needs to be replaced.

TCM Reprogramming (VCI required) → After replacement/repair, adaptation and Park Learn must be performed.

Gateway (Serial Data Gateway Module) Inspection → If P1967 recurs, the module may need to be replaced. <== it may have recall

If the solenoids inside the valve body are sticking, or if there is an oil pressure issue (sludge/contamination), the gear selector valve may fail to operate properly — and this can trigger multiple communication errors.

This is only my personal observation.

 

One week later the prescribed repair via GM Tech’s consultation with my Dealers Tech was a software program/reprogram.
All was well upon my picking up yesterday. Hopefully, longterm as well…

 

Hopefully that’s it and it runs well.

 

What is a software anomaly? Software afaik does not modify itself. So, either there's a version of the DCT software out there that is perhaps buggy but that begs the question, why does the problem not surface immediately? Perhaps what GM is doing is updating to a version with looser tolerances for sensor values. If that is indeed the case, is this sensor drift limited so that it does not continue to drift beyond the modified firmware range checks or are we looking for future failures of a similar nature?

 

Perhaps? Do you have anything at all that leads to this theory?

 

Are these transmissions similar to a Nissan GTR? Do GTR’s have these problems? Why GM?

 

Maybe it learned something incorrectly over time
On a positive note, no parts, no dct change...
Good news!!!

 

But I do have an extensive IT/Electronics/Hardware/Software background....

 

As Long as they're not just kicking the can down the road.

 

Did you have to pay for this? Wasn't it covered under the 5 year power train warranty?

 

Yes, unfortunately had to pay. Software is not covered under powertrain or extended Platinum Plus plan.
The good news is it was only $385 AND car is behaving normally once again🤞

 

This is a very interesting thought. And would mean that the issue was caused by a hardware issue, not software.

Wasn't there an issue with headlights or daytime running lights caused by (I think) an out of tolerance ambient light sensor voltage that was corrected with a software update in some cases (others replaced the sensor)? If my recall is correct, that would be an example of what you described. It may be however that some just speculated that it could be corrected with software upgrade.

 

So, isn't the 'software' embedded in the powertrain computer? How is it excluded? Crazy how they nickel and dime the customer.

 

Tough to image these cars as long term cars.

 

It would be great to know the nuts and bolts of this one. It almost feels like a typical 'reboot the darn thing and see if that does it' fix.