Was getting P0700 & P0868. Took to dealer. P0700 Transmission Control System Malfunction and P0868 Transmission Fluid Pressure Low. Dealer found almost quart ATF low from last dealers. 10 mile test no light. On the way home light came back on. Checked with my OBD Spit code P0700 , P0868 but also P0869 Transmission Fluid Pressure High (How can it be both) but also P2724 Pressure Control Solenoid "E" stuck on. No drivability problems at all. Seems like I'm backing up. Any ideas. Have dealer appointment Thursday (booked tomorrow. Wondering if serious, planning to drive 65 miles round trip tomorrow .

 

If no driveabilitu issues why were you checking codes? Check engine lite ?

 

Yes Check engine lite. Went in this am with P0700,P0868. On way home from dealership check engine lite came back on withP0700, P0868 as before but PO869 and P2724 added. Check P2724 eliminated Wrong gear, no gear, limp mode, no speed. Checked goes above 4th gear at 45mph, also on top took to 85mph and got all 8 gears. No drivability problems. Drive hour each way just to go to Tech been Corvette only for 28 years same Dealership, so feel comfortable. Guess I'll take 65 mile trip tomorrow, see dealer Thursday. Thanks for the reply. Fran

 

Probably a dumb question. So in the 1980,s I used to get all this CEL stuff usually related to emissions generally in American pickups. . Then After that decade driving mostly new Japanese stuff and classic corvettes-CEL codes and were never an issue. Now this CEL seems to have come back in style. Until I got my new c8 I never k new about CEL stuff that was related to transmissions. So we hear about all of theses people trying to decipher codes and driving back and forth dealers and talking to the- on star lady- making us jump through hoops! . So with all this wonderful tech couldn’t the cars computer tell you in English a general description of what’s wrong with your car or at least have a translation in the owners manual ??l. Tech is great but this stuff seems awful silly and expensive just to shift your transmissions gears which we have all been doing for years without lights and codes and it was more fun…

 

You are so right. I had 2 Tire and Service Center for 36 years. Labor rate was $25. Hour. Things are so over 😪 technology. Oh well another 2hr (both ways) Thursday.. Thanks Frank

 

I had similar codes on mine. Dealer first tried to do the DCT flush which unfortunately did not resolve the issue. So they then had to replace one of the valve bodies inside of the transmission. With the valve body replacement, they also replaced the internal filter, the external filter as well as all of the transmission fluid. This cleared all of the codes and so far so good. 🤞

I had this service completed at a very reputable Chevrolet dealership that specializes in Corvettes. They have one of the best Corvette techs in California and they are Corvette fanatics. They told me that in their experience, it doesn't take much to plug up a sensor or solenoid, even microscopic particles can cause these types of issues and codes. If the flush can't dislodge the particles, they have to end up replacing the valve body. The whole process didn't take long, maybe 3-4 hours while I waited for the vehicle.

This issue didn't sour me at all about the car or transmission. Both are awesome. It was a minor inconvenience and hopefully GM/Tremec is learning more about these types of issues and will make changes down the road to the valve bodies to make the sensors/solenoids less susceptible to microscopic particles.

 

The codes do not necessarily tell you what is wrong. They say things like "low pressure on sensor 4". Even if you knew where sensor 4 was located in the transmission, you would still not know what is wrong, nor what will be required to fix it. The tech won't either. Instead, the DTC will index diagnostic procedure, or procedures, that will eventually lead to a proscribed solution - such as replace the valve body, or replace the transmission, or perform a hydraulic system flush, then test again. So, I think that is the primary reason you dont get a clear explanation of the problem - its because it is not known until further diagnostic are performed.

There's pages and pages and pages of DTCs listed for the transmission. Here is an example of a procedure for codes P0867-P0869. Notice it lists or points to some diagnostic instructions. It list the descriptor and says it related to pressure sensor 3 and solenoid valve 5. It give the condition for setting it, any actions the car may take while is set (in some cases a feature such a idle creep may be disabled), and it give conditions for clearing (some will clear automatically). But it does not say what is wrong because its not known until the diagnostic procedure is performed.

I agree it is largely due to the complexity of new systems compared to those of yesteryear. But I dont think this is so unusual. In the past if your car ran rough - the tech did not know if it was fuel, igntion, something else,until some diagnostics were performed. The new tech will sometimes identify an issue with igntion, a spark plug misfire, a problem with fuel pressure, etc. We did not have that in the past.

 

Hey thanks for explaining how the Code/CEL system works. I thought it was a bit more capable of self diagnosis than it really is.
Perhaps it will be refined in the future. A modern computer is much more intuitive and easy to operate than one from 25 years ago!!

 

Good luck at the dealer. Hope the repair ends up being relatively minor and you can get back to enjoying your car.

 

That’s what warranties are for let them read the codes.

 

Owned 2 Tire & Service Centers 36 years. Hate to drive 25 miles each way if I can fix in my garage. Thanks for the input 👍 Frank

 

Ya know, that's an interesting thought. When I first read it, I was thinking that's never happening, because the diagnostic procedures require the use of the computer in the shop and involve running additional tests. Had I stopped thinking at that point, I would not have responded further. But - for example - the hydraulic system flush is in many cases the first thing called for in the diagnostic procedure. Once performed, if it solves the problem, you're done. That procedure involves a computer manipulation of the solenoid valves with the engine running, with a goal of freeing trapped debris and moving it to the filter, after which, I believe, the filter should be changed. Those who had it done, successfully, to resolve an issue have reported on the forum that the filter was changed after the flush. So - though maybe a little far-fetched - it seems feasible to put the necessary software on board to execute that flush. Much like initiating an OTA, the owner would be invited initiate a built in diagnostic process, but to leave the engine run during the process (one forum member reports it takes 20 minutes). After which the system could check to see if the problem is solved. And then the owner would be prompted to have the Transmission Fluid External Canister Filter replace now. I can think of pros and cons to this idea. But I'll leave it at that.

 

Have 10:30 appt at dealer. I'll see what they did when sign invoice. Thanks for the input Frank

 

Sounds like contaminated solenoids.
I'd try a x3 flush procedure and a DCT filter swap.

 

I could be wrong, but I believe the vehicle must be on a lift to perform the flush procedure as the DCT engages different gears/solenoids.

 

I don't know. Jerry U frequently posts his photo of that process being performed. Maybe he will post it again. But it would not change the idea. It is possible that certain additional procedures could be performed on board (if not this one, because it require gears to be engaged). With AI it might be able to put it all together. Right now when I read some of the procedures, they say things like (to paraphrase) if this DTC is set, but these two are not then do this, or else do that. So the procedures seem to include sorting through a combination of DTCs that might be set to reach a conclusion. Some of that could possibly be built in - one day. Not saying its a good thing, or bad thing, it was just thought based on a comment someone made.

 

I've seen pictures where it appears the wheels are on the ground when the procedure is performed. I don't believe the wheels turn.

 

Just left dealership. Did DCT flush, replaced filter. Lite came on in 25 miles. Have appt on 12th for top rattle (5 visits) and they said if #5 solenoid replace have to send to manufacturer. Said they not allowed 🚫 to go inside tranny. If so because that will be visit #3 according to Virginia Lemon law have to refund or replace. Don't want refund but will ask for expedited replacement. Love my Yellow LT3 so hope this fixes. Will post fix .Thanks for input. Frank

 

So, here is what a solenoid valve looks like. It appears to have a solenoid that actuates what appears to be a plunger, with some red things that may be o-rings or similar gaskets. And also where it goes, position 5, in the Main Control Valve body. Looks like the plunger part fits into the valve body. I wonder, are they replacing just the solenoid, or are the replacing the entire valve body? I have read forum reports about replacing the entire valve body. Seems to me that could not just replace the solenoid without insuring the valve body is free of debris. So does the dealer do that, or do they ship the whole valve body back?

 

I'm a little confused on a couple of fronts. If they can't go inside the tranny because of the lemon law, how on earth are you going to get it repaired?
If they are just not allowed to go inside the tranny, again, how on earth are you going to get it repaired? To get to the valve body (which contains the solenoids I believe) you just have to remove the oil pan.

In my post #6 above you will see I went though a similar issue. They ordered the appropriate valve body and when it arrived, swapped it out as well as changed the internal and external filters and replaced the transmission oil. It sounds to me like your dealer really doesn't understand how this is repaired or I am misunderstanding your post. And no, I don't believe they send the valve body to the manufacturer - they just replace it. They may, however, send it after the fact to dissect it, but it should just be replaced. Only took them around 3-4 hours to do mine. It might be time to find a new dealer if they are giving you the runaround.

Edit - the part number for the valve body they replaced is 24045740