P0720 Transmission issue

[ffrh911]

2004 infiniti fx45
I am posting this in the general forum because there is not much support nor many people on the fx forums these days, and I also believe my problem isn't centralized to the fx vehicles.

Transgo shift fix installed over 2 years ago.
Started getting the p0720 code when driving the other day.

I found that the output speed sensor was having a delay on acceleration and wouldn't show rpms until it was around 3000rpm and then would finally register the rpm and would shift.

I pulled the transfercase and replaced the OSS. No help.

Driving yesterday I noticed that when cruising, the input and output speeds match, but the speed showing from the TCM is only at 39mph no matter how fast I am going. And then when I stop, it shows I'm going 170mph!

The ECU of course shows the speed correctly.

Anyone have a similar issue? I mainly see that code relating to the transmission being stuck in one gear and can't find anything related to my situation.

Appreciate any valve body recommendations too!


Please help!