Over the past 2.5 months I've been trying to fix what was originally a P0720 error (indicating speed sensor failure). When this first occurred I talked to a local transmission shop who said 3% of the time it's the speed sensor, 97% of the time it's the TCM/Valve Body.

Ok, so first step was to order a used Valve Body/TCM and new OEM speed sensor which I put in and worked... sort of. The car drove but had hard shifting from 3 to 4 and slipped into 5 with increased RPM. I figured I got a bum used unit with solenoid or TCM issues so I returned it and having researched the issue more decided to just get a new TCM to put on my original valve body. The "internet" says that the TCMs for a variety of Infinity/Nissan models are interchangeable so I ordered one of Amazon that was good for G37's all the way up to the newer Q models.

I got the TCM and put it in my car with the old valve body and it worked for about 2 minutes shifting into 4 and 5 (yay) and then after stopping at a light and then going again fell back into the won't shift past 3rd issue. So I figured then, wow, I have some horrible luck so I returned the TCM and speed sensor, and ordered a new speed sensor and another used Valve Body/TCM thinking maybe my original valve body was the issue.

Replacement parts came, put them in and same issue... won't shift past 3rd. After more research a nagging thought entered my mind that perhaps the newer Q model TCMs weren't really compatible with the G models.

Had the car towed to an Infiniti dealer (which I had really been trying to avoid) for them to hook up to a consult and flash/reprogram the TCM if needed. Dealer service department said we can't detect the TCM so there's nothing we can do... waste of time but hey, I got a $185 dollar car wash for their troubles. Towed the car back home.

Hit up YouTube to watch yet more videos, including one where the guy was swapping out the V30 transmission from a Q model into his G and noted that he swapped the TCMS... ah ha!! Hit the guy up on Instagram to ask why he did that and he responded saying yeah... the Q model TCMs aren't compatible with the Gs... another ah ha!!

So today I just received another TCM which I confirmed with the seller before they shipped matches the Serial/Model number from my 2013 G model (also figured this out from some YouTube videos on how to identify this) so I'm really confident that I've finally solved this problem and pull everything apart again and swap out my "original" TCM with this replacement on my "original" valve body... let's hit the highway right? I literally had Tom Cochrane "Life is a Highway" cued up on my phone for the test drive.

But nope... didn't even get past the end of my street realizing that it still won't shift past 3rd... w the ever loving f...

To summarize... car failed at the beginning of September about 150 miles from my house with a P0720 ODBC code, after many attempts at fixing now have my original valve body (the cast aluminum part) with a different used "matching" TCM and brand new Hitachi OCM speed sensor... and the car is essentially back at square one.

I'm thinking now that I perhaps need to take it back to Infiniti to have the TCM flashed/reprogrammed but according to the Internet these should be plug and play... but then again this is the same Internet that told me the Q model TCMS were compatible.

Has anyone else gone through this? Can anyone offer some insight or help on this? Thanks in advance...

 

Do you live anywhere near Hardyston, NJ? If so, shoot Pat at Level 10 an email: trans@levelten.com

 

Finally got this resolved... replied to another post where Snaxxor has a great reply to confirm what he says and add details to what finally worked for me.

https://www.myg37.com/forums/engine-...ml#post4303792

 

so the issue was that you needed a 2013 and earlier TCM/valve body?

is yours the 7 speed AT? how are they different?

 

It seems that the issue I had was specifically the valve body and not the TCM. I'm not going to pull everything again and confirm by putting a new VB with my original TCM to test but essentially my order of repairs was:

1) Replacement VB/TCM combo worked with shifting issues...
2) Swapped solenoids to see if it would improve but no change
3) Put original VB back in with new TCM but TCM was from Q model... didn't work
4) Ordered another VB/TCM combo that didn't work... but realized it was from a Q model
5) Ordered a TCM from a 2013 model and put it on original VB and didn't work
6) Finally got a VB/TCM combo from 2013 model and it worked

Process of elimination tells me that perhaps a new VB with my original TCM may have worked but I am "done" lifting, draining, swapping at this point... haha

Thankfully all the parts I tried were returnable...

 

And yes, I have the 7AT... really not sure how they're different except that when I had the VB/TCM in the car that came from a Q model (I know now based on the serial numbers it was a 2016) and took it to the dealership they said they couldn't even determine the part number or communicate with it. Together with the fact guys are swapping TCMs on the Q model V30 transmissions they're putting in their Gs confirms they're just not compatible.

 

is your tranny fixed?

 

Yes, details in thread above.

 

good good

 

Hey man im running into this issue now when you got your new valve body and tcm did you have to go to the dealership to have them reprogram it and install it or was it just plug and play?

 

same exact issue as him, i replaced my tcm from a 2013 model and didnt work, im about to change out the valvebody too with the matching tcm. reply or dm me on ig @g37.dom ill lyk if this worked.

 

Hello. Where did you order the valve body from? I've similar issues with my car. The dealer told me to replace the valve body and wants to charge me 2800 for it. Thanks

 

hey bro can i get the link to buy the VB/TCM from 2013 model

 

Did you end up buying a VB/TCM? I seen in a different thread that he purchased from fivestartransmissionparts.com.

Here’s the link to the other thread.

https://www.myg37.com/forums/engine-...ed-sensor.html