I took my 2020 c8 with 23,000 miles in for it's 4th oil change and when I tried to back the car out of the garage it wouldn't go into gear and the engine trouble light came on. I tried a couple times and the third time it went into gear but the engine light remained on. The dealer came up with the code P0700 and told me they are going to replace the transmission. The engine light is no longer on and the car seems to drive normally for the past two weeks while I'm waiting for the transmission to arrive and be installed. My diagnostic tool showed a P2850 and P0700. Has anyone else run into this situation?

 

From what i found in regards to other DCTs from other manufactures, that code means, Shift Fork "D" Unrequested Movement. Me personally I would monitor it for a while longer to see if it comes back. If it keeps happening at any frequency then have the transmission replaced. In my opinion, this looks more like a one time glitch as oppose to an actual problem.

 

Regarding the tranny problem, happy to hear that it is a mechanical issue and not a biological issue.

 

Did they change the tranny fluid at last oil change? Had friend with 2022 only 5000 miles drove to work mo issue got a text to bring car in immediately due to tranny issue. Started car check engine came on went to dealer they said needed tranny replacement. I told him sounded like a glitch andvtell dealer disconnect battery for 15 minutes they didnt listen. Especially since car drove no issues even after check engine light. They changed tranny. No it shows on Car Fax. I would wait to see if it happens again. Seems like a computer glitch.

 

I took a look at the Service Manual. P0700 I think is a informational DTC that indicates that the Malfunction Indicator light is to be set. I think it is triggered by another DTC, that indicates more about the actual issue. In this case P2850. I looked at the procedure called for by that code. It seems to be an indication of unrequested movement of the on or more of the shift forks (there are 5 listed). It calls for a few diagnostics. One is to check fluid level and condition, and correct if needed. Then is says clear the DTCs. If the DTC comes back, it says - Step 10 - Replace the component T12 Automatic Transmission. So, while I cannot be sure that this all that the tech found, this particular instruction seems to call for replacement of the transmission if the DTC (P2850) come back. I also says if the DTC does not come back, step 12 All OK. I would think that if the code P2850 came back, or comes back, then it would (eventually?) cause the MIL to be set again. Since you have your own tool, see if that code P2850 is still there. I would probably try to ask the dealer or tech more about why they say the transmission needs to be replaced. By the way, there are many, many codes related to the transmission. Many of them have longer diagnostic procedures and end with replacement of a valve body. The P2850 seems to be a bad one if it is real.

 

did you allow the car to idle down before placing in reverse?

 

Lol

 

I think you hit the nail on the head. I think it was just a quirk. I've driven it at least 500 miles since the episode and still no light and nothing peculiar. I will keep my eyes on it and since it's under warranty I might as well have them replace the transmission. Thanks for your reply.

 

Yes another member feels the same way as well as myself. Thanks for the reply.

 

Yes I always let it drop to 600 rpm before engaging reverse gear.

 

It took them 3 days to finally tell me it needs a new transmission. Long story short the third day I decided to push the service manager. He said they're overwhelmed with car repairs and only have two certified transmission techs and that's the delay. I think in the end knowing I wasn't too happy about the lack of attention the car got I feel they made the decision to just replace the transmission. I agree with a few of the other members saying it was probably a one time glitch.

 

Up til now, based on other threads, I have been under the impression that a big repair like this, replacing a transmission, would always involve the review by GM factory rep. That is, some others have stated that the dealer said there was a delay because a factory rep was consulted or involved. Not saying thats always the case. But, did your dealer say anything about a GM rep being involved? I'm wondering too, is the new transmission on order? What will you do when they ask you to bring the car back for replacement? If you decline the replacement, I wonder if that would affect future claims if you have another transmission problem later?

 

Good point. After all the great replies I think I will call corvette concierge to see if they can direct me to the right party. As others have mentioned I'm concerned about the service techs at the dealership and if I do have the transmission installed will it be correct. Thanks again.

 

If a SA told me that a 'transmission tech' was going to replace the DCT in my C8, and not the 'Corvette Specialist', I think I'd mosey on down the road to another dealership.

 

I have the issue too, p2854E, new 2023. Also, when I am in manual mode on the highway, in a higher gear, there is a "thud" in the car when I slowly depress the throttle. Anybody else experience a thud during slow depression of pedal in higher gear on highway? It's a more harsh "thud" when at lower RPMs (2500-3000) and doesn't happen when I quickly depress the pedal.

 

how long did you take for waiting valve body order?