Guys I really hope you can help me. I know there are thousands of posts about or mentioning this code but I cannot find the specific answer for my specific issue.

After a few cycles (Drive and park, drive and park)eventually I will get a check engine light (CEL) and my transmission starts shifting very hard from first to second. I do not lose high gear or get stuck in a gear. I am aware that the TCM has sent a message to the ECM which triggers the CEL and results in the transmission going into Max Line Pressure resulting in the hard shift.

Other than the CEL and effects of it, everything runs and works fine. I recently had the transmission completely rebuilt to a stage 5 and had the torque converter rebuilt, reinforced and made more efficient and using upgraded products. Both had no expense spared to get the best parts.

Given this information, everything works and functions great. The only problems are the result of the CEL and the default actions that come from it. If the TCM did not send a code to the ECM which triggers the rest there would not be a problem. So why is the TCM triggering the ECM?

Does anyone know why the TCM is sending a code to the ECM resulting in the P0700 only. This is the only code I get, no others.

Please help me figure this out. I am having it put on a bigger diagnostic machine tomorrow to see if there are any codes in the TCM only or the ECM that mine does not see.

I carry a scan tool with me so if the CEL comes on I clear the code while I drive and everything is fine again for a few more cycles which always vary.

 

I don't fully understand the reason behind this one but it is similar to yours except stuck in 2nd, so may help. Post 9 has the "answer", if it is indeed "the" answer. Good luck.

https://www.corvetteforum.com/forums...-2nd-only.html

 

This is where real mechanics make their money.
Lets go through the process. First, it's not a sensor or harness problem. You would have a circuit or component code. What's left, a mechanical problem. If the transmission's oil pump puts out inadequate pressure or there are one or more clutch packs that are worn. an algorithm called the clutch volume index is calculated by the pcm and sets a general P0700 code.
Examine transmission fluid, look for a burnt smell. If positive it will be best to get a professional opinion.

 

Transmission was completely rebuilt a month or two ago, all new Alto Frictions, Kolene Steels, Sprags, Beast Sun Shell, all new solenoids, TransGo Reprogramming Kit, High RPM Springs, High RMP Pump components, everything was replaced and all upgrades done including new vale body plate and you name it it was done, torque converter was also redone and had the fins welded to make them stronger and all those goodies were done.

It is not stuck in any gear. It runs and shift great but after several cycles it will eventually throw the P0700 code which results in the CEL and the trans going into max pressure resulting in hard shifts. I do not lose or get stuck in any gears. The Max pressure and hard shifts are a result of the CEL which is a result of the TCM telling it something but what? Could the TCM be bad?

It gave me this code and that is why I had the Torque Converter and Transmission rebuilt to begin with, after having that done, still get the same code.

 

OK, well, Post #9 said that the problem was the key FOB or a low battery in the Key FOB so I put a brand new battery in my FOB, if that does not change anything I do have a new FOB That I can have programmed so I can try that in case there is a problem with the FOB itself. I have to have mine programmed because it will not recognize it when I try so I will have to have the Stealership do it for me. If after that there is not a solution then I will keep checking other things. Not sure how that has anything to do with anything but hey, stranger things have happened I am sure.

EDIT:

I also just changed my driver side rear hub and speed sensor because it was making a roaring noise, I have not driven it much sense so I wonder if that could have triggered it or be related. I just wish the P0700 code was more damn specific.

 

P0700 code just tells the ECM that the TCM detected a fault. You need to use something as powerful as the Tech II to get into the TCM to read its fault codes. My guess is your TCM is bad, but thats just a guess, the Tech II should find the fault.

 

That is what I am thinking, before I was getting the P0700 and the other code which I forget the number but it was the Trans Component Slipping Code. Since the rebuild and upgraded parts, I no longer get the Trans Component Slipping code just the P0700 code and there is no rhythm or rhyme as to when it happens.

 

What are you using to extract codes, an OBD2 code reader? If this is the case this is pointless. Those readers only give you emissions related info ,not transmission.
You're asking for help and not providing the information necessary to help you.

 

Yes that is what I am using, I guess, it plugs into the OBDII port on the driver side and it reads and clears codes, like I said tho I am going tomorrow to have the mechanic put it on his diagnostic machine and he is going to pull everything with it so maybe that will give me more information.

If I used that to clear the code and there currently is no CEL or code, when he puts it on his machine will it pull the stored codes or do I have to have a current CEL to check it?

If you do not use an OBDII to check them what do you use? Or suggest I have someone use. You always hear people say have AutoZone or advance check and read the codes, so is that not what they use and is that useless?

 

Hey dude, those code readers give but a glimpse into the diagnostic information available from your PCM. What do you expect for $50. That's why it's free at Auto@#%. Your avg tech has several thousand dollars in diagnostic equipment to access the many modules in your vehicle. Engine transmission, abs body controls etc. Even the switches on your door need to be programed.
After your visit to a real mechanic let us know the codes they extract.

 

zali0104, a good indy mechanic will have this equipment, correct?

 

Since a Tech 2 is GM specific, do I have to use a Tech 2 or a scan tool equivalent to that? My friend has a large diagnostic tool that cost like $5000 is that what you are referring to something like that? A generic equivalent to the Tech 2?

 

Diagnostic equipment for cars can get out of control for a service tech for multiple makes. Over the years I have accumulated maybe $20.000 worth.
For GM cars the weapon of choice is the Tech 2 though very expensive, if you wanted you can buy a chinese clone from sites like AliExpress for $300. that can turn you into a hero.
They look and work like the real thing. Will be more than adequate for the home mechanic.

 

What I would give to be close to you and be your friend. It is hard to find someone that knows what they are doing much less one that will make the time to help you. I know several people around here that have the tools and when they need their friend me to do something I drop what I am doing and run but when I need something (Rare cause I prefer to not bother anyone) they tend to be too busy or just forget to call or text me back. Oh, until they need me again.

 

I found this, does this make any sense to anyone, I hate when someone knows or seems to know the exact problem yet they do not share that part of the information.

Circuit/System Description
The transmission control module (TCM) uses the (GMLAN) to signal the engine control module (ECM) that the TCM is requesting malfunction indicator lamp (MIL) illumination. This happens when the TCM has determined that a failure affecting emissions has occurred in transmission control system. When the ECM receives the a message from the TCM, DTC P0700 will set.

 

Basically this is what i'm saying. codes that little reader cannot pick up exist. The reason you need to see a mechanic with the proper tools.
Request a printout and post it.

 

and your not taking it to the people who rebuilt the tranny? why?

 

Can't blame anyone without proof, that would be the transmission codes

 

I am taking it to the transmission guy to have his machine read the codes, and I now have an appointment with my Chevrolet Dealer Friday at 1pm to have it put on their Tech II also. So by the end of day Friday I will know something, and I will post it here and maybe we can figure it out of they will tell me the problem and the solution. Thank you all for your help, stay with me so we can hopefully finally solve the P0700 question of all time.

 

This will have to take a short break, the code was not thrown when my mechanic checked it and his machine found no code and nothing in history. My local dealer will not have a Corvette tech there until July 1, and last night at the drag strip I broke the 3/4 clutch pack, so it is at the transmission shop getting rebuilt again. Really makes me second guess Alto Red Eagle Frictions and their 3/4 Clutch packs.

So after the rebuild if I am still getting the code I will let you know, if not, I will still let you know.

Rick