Is anyone documenting the transmission issues for the C8 corvettes?

Just bought my 2021 with 3100 miles on it, has 3500 now, and code P2818 popped off (solenoid 8 stuck open).

For me, this means that the transmission is shot if debris is making it past the filter somehow and clogging up the solenoids.

Taking it in tomorrow and I suspect they will warranty a transmission flush and filter change first.

My GM engineering sources tell me that the MY20/21 especially had transmission issues. Which brings me to my original question, is anyone documenting this?

 

So P2818. Solenoid 8 is stuck open.

The dealer told me my calibration was out of date and that was the issue. They charged me $200 and kicked me out the door.

My background: thermal systems engineer for a very big tier 1 supplier.

My GM engineer friend and other automotive engineering friends are finding it hard to believe that an old calibration made the #8 solenoid get stuck open. I agree. The only thing that could make a solenoid get stuck open is debris.

 

That should have been a warranty repair and no charge to you.

If the code comes back, your dealer should perform a hydraulic system flush and change the external canister filter...again, under the 5/60 powertrain warranty.

 

In the 2020 manual that I have, here is the diagnostic procedure for that code. It could have been revised. Where it calls for the "cleaning procedure", that may have been replaced with the Hydraulic System Flush procedure but I do not know that. Also, there could have been transmission software updates that would not be called out in this procedure. The procedures seems focussed on clearing debris, but you can see that if and when the DTC is cleared and does not come back, its done. So if they did update the software, and the DTC went away, they would be done.

Circuit/System Verification
1. Verify the following conditions do not exist: Low Fluid Level - Refer to: Transmission Fluid Level and Condition Check
2.
If a condition exists
Repair or replace as necessary.
3.
If no condition exists
4. Ignition >> On / Vehicle >> In Service Mode & Engine >> Off
5. Perform the following action: Clear the DTCs.
6. Ignition/Vehicle >> Off - For greater than 60 s
7. Operate the vehicle within the Conditions for Running the DTC. You may also operate the vehicle within the conditions that you observed
from the Freeze Frame/Failure Records data.
8. Verify the DTC does not set.
9.
{ Test failed 1> time(s) } If the DTC sets
10.
1. Perform the following procedure/test: Limited Slip Differential Clutch Hydraulic Control System Cleaning Procedure - 3> times
2. Repeat the procedure starting at step 3>
11.
{ Test failed 2> time(s) } If the DTC sets
12.
1. Perform the following procedure/test: Transmission Oil Filler or Drain Plug Replacement & Automatic Transmission Fluid Filter
and Seal Replacement
2. Repeat the procedure starting at step 3>
13.
{ Test failed 3> time(s) } If the DTC sets
14.
1. Perform the following procedure/test: Automatic Transmission Fluid, Fluid Pan and/or Filter Replacement & Automatic
Transmission Fluid, Fluid Pan and/or Filter Replacement ( Main )
2. Repeat the procedure starting at step 3>
15.
{ Test failed 4> time(s) } If the DTC sets
16.
1. Replace the component: T12 Automatic Transmission
17.
If the DTC is not set
18. All OK.
Repair Instructions
Perform the Diagnostic Repair Verification after completing the repair: Diagnostic Repair Verification
Automatic Transmission Replacement - T12 Automatic Transmission Assembly
For control module replacement, programming, and setup refer to: Control Module References

 

When was your 2021 put into service? You may be past the 3 year DTC fluid change requirement?

 

So update.

Talked to a few people in the industry and there is definitely debris clogging the solenoid. Aka the trans is shot.

I explained this to the dealer and they told me that it has to happen multiple times before they will open a TAC case to then maybe warranty the transmission.

What kind of warranty is this. If the solenoid sticks open…it’s because of debris.

 

I have only seen a mileage requirement for the trans filter

 

DCT fluid replacement is required every 45k miles or 3 years, whichever occurs first, per the owner's manual normal maintenance schedule. A lot of 2021s are at/near their 3-year mark, while all 2020s are beyond it.

 

The DTC filter must be changed at 7500 miles then 22,500 miles then every 22,500 miles. The transmission fluid must be change at least every three years (regardless of mileage), at 45000 miles, or when the FLM says so, or every 24 hours of track use, whichever is first.

Did you have a DTC? Was it cleared? If so, did it come back? Is the car working now without issue? I posted the procedure for you. It could have changed. But it goes through a series of progressive remedies. If any solve the problem, then its done. It does not go directly from a DTC to a transmission replacement - that is not going to happen. There is nothing more to do unless the DTC or the car is not functioning properly. I do believe that the work they did, whatever they did, in response to the DTC that you had is under the powertrain warranty - and that should have covered what they did. The PPP (aka extended warranty) I think excludes diagnosis unless a problem is found.

 

Understood. I just believe that the issue can’t be remedied by a reflash based on expert engineer feedback (aka the team who designed the parts). It will come back.

I am also sad they didn’t warranty it. They said that since the remedy was related to the ECUs it wasn’t covered under the powertrain warranty.

 

Oh. Unfortunate, but I think its consistent with the terms of the warranty. But, the "calibration" being "out of date" may deserve a some investigating. There have been some GM bulletins about communication issues that requires an update - there could be others. I don't keep up with that stuff. But certain issues might not be considered a "warranty" issue in the first place - but something they fix or should fix at no charge. How does calibration get "out of date". It implies there was some kind of update. And, if something was working before, how could it stop working just because an update existed? You may never get an answer. But to restate - you are saying all they did was update something (maybe the ECM or TCU might be worth finding out) and that fixed it or, at least, the DTC did not come back? What prompted them to check the status of an update - is there a bulletin they can show you? .........

 

mbuchan1 When was your 2021 C8 put into service?

 

There are many things besides debris that could make a solenoid valve stick open. But I agree that an old calibration is not likely the reason although not impossible.

 

I just bought it from the prior owner on June 5th. He bought it and picked it up 3/29/2021.

I'm going to go ahead and get it flushed now. Should I changed the filter too?

 

now the code does stipulate that it saw high pressure (pressure sensor) which they say means that it is stuck open. Maybe something else happened with the pressure sensor that required recal?

 

We can speculate, but when a DTC says a valve was stuck open, how does it know? It uses a sensor for that as noted. And it compares it to threshold that is exceeded for a time limit. Its possible that the threshold was adjusted, or the time, or some other software glitch or calibration actually did cause it. The car is so complex. Its not clear to me actually that debris would keep it stuck open, unless we think the debris is trapped where the valve can't shut. But maybe the solenoid itself just temporarily failed. Its why they reset stuff and see if it comes back.

 

exactly, you made me start thinking about it a bit more. The solenoids in these are very robust. So it is very possible that a cal could fix it by changing thresholds and limits. I wish they released notes for software revisions hahah

 

When you say "flush" you mean a drain and fill (replacement) of the fluid right? There is no "flushing" associated with that procedure. Don't ask the dealer for a "flush". Ask for a fluid replacement if you want that.

There is a Hydraulic System Flush but that is associated with the DCT filter replacement.

Both fluid replacement, and DCT filter replacement (which will include the HSF) are remedies that often resolve issues like this. I would consider it in your situation - maybe. If the DTC comes back they will eventually pursue those remedies, but it might be at your expense anyway unless it fails to solve the problem - and they go to replace transmission. @RKCRLR has more insight into how that part might work. I think if a diagnosis lead to a repair of a covered part, then the diagnosis is covered. But its technicality - in this case - the remedies must fail - to lead to replacement of the covered part.

There is one more step - its in the procedure I posted - where they actually remove the pan and clean it and replace the internal filter too.

 

yes, as previously mentioned by someone, GM says to change the transmission fluid every three years anyways. So I might as well replace the fluid and filter. Especially with this code popping up.

 

There are a few of us documenting our transmission issues/repairs/experiences over in the C8 General subforum. The end result of most of these stories is a DCT replacement.