I have an 08 g37 coupe with the 5at and literally the second it hit 150k miles it stopped shifting and threw a cel. I used a launch obd2 reader and it doesn't recognize the code being thrown. I changed the transmission fluid a little over 2 weeks ago so I don't think that's an issue. Anyone have any ideas on what it could be?

 

I don't know if this will help or not but the AFS light came on at the same time

 

1) Will it not shift into 5th using DS/Manual Mode?
2) Did you perform the fluid change yourself or through a mechanic/shop?

If possible, you may want to take the car to have AutoZone or someone with a better scanner to check for codes (or, look into OBDFusion or Torque apps).

Right now the issue points to the TCM (Trans Ctrl Module) with AFS being a symptom, not a cause, of a "failure." Knowing what codes are being set will help narrow down what is going on.

 

It won't up or downshift using either automatic or manual mode. I did the fluid change myself so I could've done something then, however the atf level is still good. For now I'll probably just take it to AutoZone tomorrow to get the codes checked. Ill have to check those apps out, thanks for the suggestion.

 

did you ever find the issue? im dealing with the exact same thing.