I may need to install a new TCM in my 2005 C6 Automatic. I use the diablo to tune my ECM and TCM currently. Is there anything special I need to do other than remove the old one, plug in and install the new one and then download my TCM tune to it or is it a lot more involved than that?

When is comes to electronics you never know, heck, you cannot even swap out the radio/navigation unit without a secret decoder ring from a cracker jack box with the matching VIN on the box.

 

TCM is in the passanger front fender area (can be accessed through the rear fender well cover without having to pull the fender), and is behind the ECM.


Silver box is the ecm, and if you look just above it, can see the Blue connector that is plugged into the TCM on the back side of the plastic part in the fender area).


TCM on the left, ECM on the right,



As for replacing the TCM with a new unit, will first need to be programmed by a dealer with Tech II to the car with the OEM tune, then you can reprogram it afterwards.

But lets back this up, since if you have a Diablo, should be able to flash the TCM and ECM back to the oem tune, then reflash them to the after market tune again if it was just a corrupt flash on the retune.


If the Diablo tuner "Bricked" the TCM and is can not be reflashed back to the OEM tune again, then get Diablo on the phone to correct the problem on their dime instead.

FYI, if the car was already tuned, and the tune was locked, then you have bigger problems on your hands, and and will need the Tune/ECM unlocked before you can make any adjustment on either the ECM or TCM to begin with. Worst yet, Dealer will not be able to re-flash the ECM/TCM back to stock, since the locked tune has also locked them/a Tech II from working with the car as well.

 

The TCM is not locked or have a corrupt tune, It is looking like the TCM is not functioning properly or may have a defect and needs replacement, so the thought is the TCM may be the problem.

So if I buy the TCM do I have to take it to the dealer and get a tech II to program it or do I have to take the car there and let them do it with the car? So do they need the TCM and the car or just the TCM and my VIN?

 

So I cant just buy a TCM and plug it in and hope to download my OEM tune to it, it has to go to the dealer?

 

Need new TCM in car installed, so they can program it/marry it to the car through the OBDII port with a the tech II.

So short of you jacking the car up in there parking lot to pull the tire, pull the fender well cover, pull the old TCM, install the new one, put the car back to toghter and then holding them push the car into the bay, or doing the install at home and having the car towed to the dealer,,,,,,,,,,,,,,,,,,


Myself, if was sure that it was the TCM that had problems, would just pull it out the car, pull the board out, and start looking for cold solder joint or pin/wire corrosion problems instead.


Chances are, you will not even need to go this far of pulling the board out of the PCM, since chances are the problem is either in the wire connector to the TCM pins or one of the wire connectors just above the TCM/ECM that has a corrosion problem instead.

Trust me, a soon as you pull the front tire rear wheel well cover and look inside, your going to know right way if the area was water flooded, and dealing with corroded wires problems or not.

Both the ECM and TCM are sealed units to a point, but if the car was a flood damage car, neither modules will water tight against that kind of abuse. As for having to be replaced, all depends if the problem is intermittent or not to begin with.

As for the photo I posted with the fender removed, that is just normal high humidity area type rust on some of the parts, and if your TCM/ECM area has been water flooded, the rusting is going to be a lot worst instead.

So on that note, pull the ECM, clean both it pins and the wire harness connector pins with electrical spray contact cleaner, reach up above the TCM connection and clean the other connectors above up, and see if that solves the problem to begin with. If you still have problems and know that its the TCM itself that is bad, then no harm. no foul pulling the TCM apart to check the soldering for cold solder joints/corrosion problems. As sealing the unit back up when you go to screw the cover back on, RTV silicon works great for that.

 

Thank you for that advice. I will do that. Personally I think that is a stupid place to put the brains of the car but I can't change it so I will just see what it looks like and go from there.

 

Agreed, stupid place to put both the TCM and the Ecm.


Also, why do you think that you need to replace the TCM?
The TCM may be fine, and the problem could be in the electrical connectors to the trans instead.

Really, just pull codes on the car, and the codes should tell you what module is having problems to start with.

 

if I remember correctly the op has a built tranny....

 

So thinking out loud, 4l to a 6l and now needs the TCM conversion.

http://www.tbmsport.com/6l8090econversionfaqs.html

 

I do have a built Tranny but my problem from the beginning was this. I bought the car and it was doing fine except an air bag light and an abs light, the guy I bought it from told me to take it to the dealer and have them fix it and he would pay the bill. He also said all the fluids were fresh but they were not so he agreed to pay for that. The dealer flushed and filled the coolant, oil, brakes, tranny and differential.

A few days after I get it home I get 2 codes, P0700 and Trans component slipping P1870 code. So I decided to rebuild it and beef it up with the best parts, all updates and all new stuff like Beast Sun Shell, Sonnax reinforced forward drum, Transgo shift kit HD2, you name it. Got it together and a few cycles of driving and the P0700 came back. A few times drag racing and I killed the 3/4 clutch pack. I had it rebuilt again, just got it back and after 4 cycles, P0700 code.

Monday it is going back and he is installing a few more things and I am replacing the transmission and differential speed sensors in hopes the P0700 will go the hell away.

If not, I am either taking it to the dealer or I have a brand new GM Crate transmission and converter I can put in it.

Ironically when I killed the 3/4 clutch pack and it was slipping like race tires on ice, it never threw a code, go figure, it would not pull a string out of a cats butt yet no code.

Since the P0700 has to do with some type of sensor/communication between sensors, I hope either the transmission or differential speed sensors I am replacing are the cause, if not it is either a loose wire or the TCM or god knows what.

It is not a hard part in the transmission, hell, they are all new almost, harness, sensors, solenoids, pistons, valves, sun shell, sprags, forward and reverse drums, frictions, steels, royal purple fluid, trans cooler, accumulators, valve body separator plate, on and on, is new.

From what I have read on the P0700 code, it has to do with the speed sensors talking to speed sensors talking to the TCM and matching speeds and rpms and so on and so on, not exactly that but you know what I mean. It has to be something electrical is my point, it is suggested it is a loose wire or an open circuit on the TCM but it is electrical not an internal hard part.

My thing is this. The P0700 is a general code since the TCM cannot set a code but it has to point to only so many things that it can be, but no one has said or knows what that or they are.

Another words P0700 code, then a tech II and in the TCM there are say 5 possible causes, if I knew those 1 to however many I would know what to check.

Why not take it to my dealer? They do not have a Corvette Tech II guy for transmissions there and can only have him there when needed a few weeks from when you tell them or bring them the car. If I drive it I clear the code to stop the max line pressure, the code has to be on for the Tech II to check it, maybe you can see the problem. If I could get the code, drive it there, let them run the Tech II, then I would. But no, I have to schedule it 2 or more weeks out and hope the code is on when I take it.

Fingers tired now...

 

I took the ECM and the TCM out of the car and took all the connections off, the 3 on the ECM and the one on the TCM. I cleaned them really well with CRC cleaner and then blew the excess off before I reinstalled them just in case. Got everything reinstalled and the car still starts so I guess I got it back right (No way to get it wrong). So with that and the changes I am having done Tuesday and Wednesday I hope it will solve my problem. I really doubt it will since nothing else has. If not I am going to drive it until the code comes on and then take it straight to my dealer and have them drive me home and just leave it there until there tech can put it on a Tech II and see what the heck it says. Maybe I can finally put the mystery of the P0700 to rest.

I spoke to 2 corvette transmission specialist that sell and specialize in corvette transmissions and they said anytime they had a P0700 code the only way they could fix it was put a new transmission and converter in it because they could never pin it down. Maybe they did not have the Tech II, Maybe the Tech II will not provide any further information on this specific code, heck, who knows, where is the Chevrolet people when you need them?

 

Not sure if I mentioned these things but here we go.

I did not cut open the TCM to check it due to the way it is made. If it had a few screws or bolts and a seal then I would have but at this point and the way it is made I did not want to chance it, yet.

Plan A: There are a few things my Transmission mechanic wants to try so it is going back Tuesday and while he does that I am also having him install the two new speed sensors, one on the differential, one on the transmission. I hope that in conjunction with what he is going to do will fix the problem and more importantly the P0700 code. If cleaning all this and doing all I have done then goes plan B.

Plan B: I am going to drive it until I get the code and then take it to the dealer and let them put it on a Tech II and see if it can pin point the exact problem. If I or my mechanic can fix it we will unless the dealer cost is not much. If we cannot fix it such as the TCM bad then I will bite the bullet and have them do it. If none of this works then Plan C.

Plan C: I have available to me a brand new, in the crate, GM 4L65E Corvette Only transmission (Correct Part numbers) and Torque Converter, all new, never mounted, never out of the plastic crate. I will have my mechanic install this and hope and pray this resolves the issue. If any of these do work, I am still considering Plan D.

Plan D: Since I have the exact transmission and converter available to me at less than 1/4th the cost, I am considering getting it anyway just in case. What do you guys think about that? My current one was rebuilt this time because I tore up the 3/4 clutch pack at the drag strip so it cannot hurt to have another one to bolt right in, yes or no? Grant you if mine is fixed I may never need it but if I don't, I can sell it for a profit anytime, right?

Thoughts?

 

*** UPDATE ***

I wanted to post a small update. After cleaning the ECM and TCM connections, mounting points and everything I took the car on several test drives in an attempt to see if the CEL was going to be triggered and if so if the code was going to be the expected P0700 code.

After the 4th drive the CEL did come on and the transmission went to Max Line Pressure. Since I have the transmission cooler on the car now it keeps the fluid cooler so the kidney kicking first to second shifts are not that bad which is a big plus. I have the car in the garage and I am waiting for my mechanic to get a bay free and I am taking it there to see if his code reader can find anything more than the P0700 code. And while it is there I am getting the other stuff done. If none of that fixes it then I am going to generate the code again and take it straight to my dealer to have them figure it out.

Will update as I go so hopefully this will be the answer to the P0700 DTC once and for all.