In the last few months the d4 light flashes and it shifts only from 2 to forth, not any where else. Now in the last week it only drives in first and throws a code 7 and 15. The 7 code says it is the shift control solenoid valve A. and the code 15 is the NM speed sensor. Well I have checked both of these and both seem to work fine. So many people say to replace the TCU, but I don't think this is the problem as it was replaced 4 years ago. I resoldered the main relay, didn't fix it. every time I reset the codes it works fine tell the engine warms up, 2 mins. then I get these codes. I think I might get these two parts, but that is as much as a new TCU. Any suggestions out there?

 

Well not knowing exactly how you tested the parts, and if you tested that the signals are going to/coming from the TCU.
You can reset the TCU, [battery cable off 20 seconds] then drive and see if the trans shifts normally until you come to a stop and start off again, then the D4 lights up and the trans shifts in the stupid mode again.
If that happens I call the TCU bad. But usually there is a solid non-blinking D4 light when that happens.